core-js Documentation

import 'core-js/actual';

Promise.try(() => 42).then(it => console.log(it)); // => 42

Array.from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

[1, 2].flatMap(it => [it, it]); // => [1, 1, 2, 2]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

import 'core-js/actual/promise';
import 'core-js/actual/set';
import 'core-js/actual/iterator';
import 'core-js/actual/array/from';
import 'core-js/actual/array/flat-map';
import 'core-js/actual/structured-clone';

Promise.try(() => 42).then(it => console.log(it)); // => 42

Array.from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

[1, 2].flatMap(it => [it, it]); // => [1, 1, 2, 2]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

import Promise from 'core-js-pure/actual/promise';
import Set from 'core-js-pure/actual/set';
import Iterator from 'core-js-pure/actual/iterator';
import from from 'core-js-pure/actual/array/from';
import flatMap from 'core-js-pure/actual/array/flat-map';
import structuredClone from 'core-js-pure/actual/structured-clone';

Promise.try(() => 42).then(it => console.log(it)); // => 42

from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

flatMap([1, 2], it => [it, it]); // => [1, 1, 2, 2]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

// global version
npm install --save [email protected]
// version without global namespace pollution
npm install --save [email protected]
// bundled global version
npm install --save [email protected]

ADBLOCK=true npm install
// or
DISABLE_OPENCOLLECTIVE=true npm install
// or
npm install --loglevel silent

// polyfill all `core-js` features, including early-stage proposals:
import "core-js";
// or:
import "core-js/full";
// polyfill all actual features - stable ES, web standards and stage 3 ES proposals:
import "core-js/actual";
// polyfill only stable features - ES and web standards:
import "core-js/stable";
// polyfill only stable ES features:
import "core-js/es";

// if you want to polyfill `Set`:
// all `Set`-related features, with early-stage ES proposals:
import "core-js/full/set";
// stable required for `Set` ES features, features from web standards and stage 3 ES proposals:
import "core-js/actual/set";
// stable required for `Set` ES features and features from web standards
// (DOM collections iterator in this case):
import "core-js/stable/set";
// only stable ES features required for `Set`:
import "core-js/es/set";
// the same without global namespace pollution:
import Set from "core-js-pure/full/set";
import Set from "core-js-pure/actual/set";
import Set from "core-js-pure/stable/set";
import Set from "core-js-pure/es/set";

// if you want to polyfill just the required methods:
import "core-js/full/set/intersection";
import "core-js/actual/array/find-last";
import "core-js/stable/queue-microtask";
import "core-js/es/array/from";

// polyfill iterator helpers proposal:
import "core-js/proposals/iterator-helpers";
// polyfill all stage 2+ proposals:
import "core-js/stage/2";

import fill from 'core-js-pure/actual/array/virtual/fill';
import findIndex from 'core-js-pure/actual/array/virtual/find-index';

Array(10)::fill(0).map((a, b) => b * b)::findIndex(it => it && !(it % 8)); // => 4

import 'core-js/stable';
import 'regenerator-runtime/runtime';

import 'core-js/stable';

import 'core-js/modules/es.array.unscopables.flat';
import 'core-js/modules/es.array.unscopables.flat-map';
import 'core-js/modules/es.object.from-entries';
import 'core-js/modules/web.immediate';

import 'core-js/es';
import 'core-js/proposals/set-methods';
import 'core-js/full/set/map';

import 'core-js/modules/es.array.unscopables.flat';
import 'core-js/modules/es.array.unscopables.flat-map';
import 'core-js/modules/es.object.from-entries';
import 'core-js/modules/esnext.set.difference';
import 'core-js/modules/esnext.set.intersection';
import 'core-js/modules/esnext.set.is-disjoint-from';
import 'core-js/modules/esnext.set.is-subset-of';
import 'core-js/modules/esnext.set.is-superset-of';
import 'core-js/modules/esnext.set.map';
import 'core-js/modules/esnext.set.symmetric-difference';
import 'core-js/modules/esnext.set.union';

// first file:
let set = new Set([1, 2, 3]);

// second file:
let array = Array.of(1, 2, 3);

// first file:
import 'core-js/modules/es.array.iterator';
import 'core-js/modules/es.object.to-string';
import 'core-js/modules/es.set';

var set = new Set([1, 2, 3]);

// second file:
import 'core-js/modules/es.array.of';

var array = Array.of(1, 2, 3);

import from from 'core-js-pure/stable/array/from';
import flat from 'core-js-pure/stable/array/flat';
import Set from 'core-js-pure/stable/set';
import Promise from 'core-js-pure/stable/promise';

from(new Set([1, 2, 3, 2, 1]));
flat([1, [2, 3], [4, [5]]], 2);
Promise.resolve(32).then(x => console.log(x));

Array.from(new Set([1, 2, 3, 2, 1]));
[1, [2, 3], [4, [5]]].flat(2);
Promise.resolve(32).then(x => console.log(x));

{
  "env": {
    "targets": "> 0.25%, not dead",
    "mode": "entry",
    "coreJs": "3.50"
  }
}

const configurator = require('core-js/configurator');

configurator({
  useNative: ['Promise'],                                 // polyfills will be used only if natives are completely unavailable
  usePolyfill: ['Array.from', 'String.prototype.padEnd'], // polyfills will be used anyway
  useFeatureDetection: ['Map', 'Set'],                    // default behavior
});

require('core-js/actual');

core-js(-pure)

core-js(-pure)/es

/* Detailed source-code truncated for AI context efficiency. */

core-js(-pure)/es|stable|actual|full/object
core-js(-pure)/es|stable|actual|full/object/assign
core-js(-pure)/es|stable|actual|full/object/is
core-js(-pure)/es|stable|actual|full/object/set-prototype-of
core-js(-pure)/es|stable|actual|full/object/get-prototype-of
core-js(-pure)/es|stable|actual|full/object/create
core-js(-pure)/es|stable|actual|full/object/define-property
core-js(-pure)/es|stable|actual|full/object/define-properties
core-js(-pure)/es|stable|actual|full/object/get-own-property-descriptor
core-js(-pure)/es|stable|actual|full/object/get-own-property-descriptors
core-js(-pure)/es|stable|actual|full/object/group-by
core-js(-pure)/es|stable|actual|full/object/has-own
core-js(-pure)/es|stable|actual|full/object/keys
core-js(-pure)/es|stable|actual|full/object/values
core-js(-pure)/es|stable|actual|full/object/entries
core-js(-pure)/es|stable|actual|full/object/get-own-property-names
core-js(-pure)/es|stable|actual|full/object/freeze
core-js(-pure)/es|stable|actual|full/object/from-entries
core-js(-pure)/es|stable|actual|full/object/seal
core-js(-pure)/es|stable|actual|full/object/prevent-extensions
core-js/es|stable|actual|full/object/proto
core-js(-pure)/es|stable|actual|full/object/is-frozen
core-js(-pure)/es|stable|actual|full/object/is-sealed
core-js(-pure)/es|stable|actual|full/object/is-extensible
core-js/es|stable|actual|full/object/to-string
core-js(-pure)/es|stable|actual|full/object/define-getter
core-js(-pure)/es|stable|actual|full/object/define-setter
core-js(-pure)/es|stable|actual|full/object/lookup-getter
core-js(-pure)/es|stable|actual|full/object/lookup-setter

let foo = { q: 1, w: 2 };
let bar = { e: 3, r: 4 };
let baz = { t: 5, y: 6 };
Object.assign(foo, bar, baz); // => foo = { q: 1, w: 2, e: 3, r: 4, t: 5, y: 6 }

Object.is(NaN, NaN); // => true
Object.is(0, -0);    // => false
Object.is(42, 42);   // => true
Object.is(42, '42'); // => false

function Parent() { /* empty */ }
function Child() { /* empty */ }
Object.setPrototypeOf(Child.prototype, Parent.prototype);
new Child() instanceof Child;  // => true
new Child() instanceof Parent; // => true

({
  [Symbol.toStringTag]: 'Foo',
}).toString(); // => '[object Foo]'

Object.keys('qwe'); // => ['0', '1', '2']
Object.getPrototypeOf('qwe') === String.prototype; // => true

Object.values({ a: 1, b: 2, c: 3 });  // => [1, 2, 3]
Object.entries({ a: 1, b: 2, c: 3 }); // => [['a', 1], ['b', 2], ['c', 3]]

for (let [key, value] of Object.entries({ a: 1, b: 2, c: 3 })) {
  console.log(key);   // => 'a', 'b', 'c'
  console.log(value); // => 1, 2, 3
}

// Shallow object cloning with prototype and descriptors:
let copy = Object.create(Object.getPrototypeOf(object), Object.getOwnPropertyDescriptors(object));
// Mixin:
Object.defineProperties(target, Object.getOwnPropertyDescriptors(source));

const map = new Map([['a', 1], ['b', 2]]);
Object.fromEntries(map); // => { a: 1, b: 2 }

class Unit {
  constructor(id) {
    this.id = id;
  }
  toString() {
    return `unit${ this.id }`;
  }
}

const units = new Set([new Unit(101), new Unit(102)]);

Object.fromEntries(units.entries()); // => { unit101: Unit { id: 101 }, unit102: Unit { id: 102 } }

Object.hasOwn({ foo: 42 }, 'foo'); // => true
Object.hasOwn({ foo: 42 }, 'bar'); // => false
Object.hasOwn({}, 'toString');     // => false

Object.groupBy([1, 2, 3, 4, 5], it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }

class Function {
  name: string;
  bind(thisArg: any, ...args: Array<mixed>): Function;
  @@hasInstance(value: any): boolean;
}

core-js/es|stable|actual|full/function
core-js/es|stable|actual|full/function/name
core-js/es|stable|actual|full/function/has-instance
core-js(-pure)/es|stable|actual|full/function/bind
core-js(-pure)/es|stable|actual|full/function/virtual/bind

(function foo() { /* empty */ }).name; // => 'foo'

console.log.bind(console, 42)(43); // => 42 43

class Error {
  static isError(value: any): boolean;
  constructor(message: string, { cause: any }): %Error%;
  toString(): string; // different fixes
}

class [
  EvalError,
  RangeError,
  ReferenceError,
  SyntaxError,
  TypeError,
  URIError,
  WebAssembly.CompileError,
  WebAssembly.LinkError,
  WebAssembly.RuntimeError,
] extends Error {
  constructor(message: string, { cause: any }): %Error%;
}

class AggregateError extends Error {
  constructor(errors: Iterable, message?: string, { cause: any }?): AggregateError;
  errors: Array<any>;
  message: string;
  cause: any;
}

class SuppressedError extends Error {
  constructor(error: any, suppressed: any, message?: string): SuppressedError;
  error: any;
  suppressed: any;
  message: string;
}

core-js/es|stable|actual|full/error
core-js/es|stable|actual|full/error/constructor
core-js(-pure)/es|stable|actual|full/error/is-error
core-js/es|stable|actual|full/error/to-string
core-js(-pure)/es|stable|actual|full/aggregate-error
core-js(-pure)/es|stable|actual|full/suppressed-error

const error1 = new TypeError('Error 1');
const error2 = new TypeError('Error 2');
const aggregate = new AggregateError([error1, error2], 'Collected errors');
aggregate.errors[0] === error1; // => true
aggregate.errors[1] === error2; // => true

const cause = new TypeError('Something wrong');
const error = new TypeError('Here explained what`s wrong', { cause });
error.cause === cause; // => true

Error.prototype.toString.call({ message: 1, name: 2 }) === '2: 1'; // => true

Error.isError(new Error('error')); // => true
Error.isError(new TypeError('error')); // => true
Error.isError(new DOMException('error')); // => true

Error.isError(null); // => false
Error.isError({}); // => false
Error.isError(Object.create(Error.prototype)); // => false

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/* Detailed source-code truncated for AI context efficiency. */

await Array.fromAsync((async function * () { yield * [1, 2, 3]; })(), i => i ** 2); // => [1, 4, 9]

class Iterator {
  static concat(...items: Array): Iterator<any>;
  static from(iterable: Iterable<any> | Iterator<any>): Iterator<any>;
  static zip<T extends readonly Iterable[]>(
    iterables: T,
    options?: {
      mode?: 'shortest' | 'longest' | 'strict';
      padding?: { [K in keyof T]?: T[K] extends Iterable ? U : never };
    }
  ): Iterator<{ [K in keyof T]: T[K] extends Iterable ? U : never }>;
  static zipKeyed<K extends PropertyKey, V extends Record<K, Iterable>>(
    iterables: V,
    options?: {
      mode?: 'shortest' | 'longest' | 'strict';
      padding?: { [P in keyof V]?: V[P] extends Iterable ? U : never };
    }
  ): Iterator<{ [P in keyof V]: V[P] extends Iterable ? U : never }>;
  drop(limit: uint): Iterator<any>;
  every(callbackfn: (value: any, counter: uint) => boolean): boolean;
  filter(callbackfn: (value: any, counter: uint) => boolean): Iterator<any>;
  find(callbackfn: (value: any, counter: uint) => boolean)): any;
  flatMap(callbackfn: (value: any, counter: uint) => Iterable<any> | Iterator<any>): Iterator<any>;
  forEach(callbackfn: (value: any, counter: uint) => void): void;
  map(callbackfn: (value: any, counter: uint) => any): Iterator<any>;
  reduce(callbackfn: (memo: any, value: any, counter: uint) => any, initialValue: any): any;
  some(callbackfn: (value: any, counter: uint) => boolean): boolean;
  take(limit: uint): Iterator<any>;
  toArray(): Array<any>;
  @@dispose(): undefined;
  @@toStringTag: 'Iterator'
}

core-js(-pure)/es|stable|actual|full/iterator
core-js(-pure)/es|stable|actual|full/iterator/concat
core-js(-pure)/es|stable|actual|full/iterator/dispose
core-js(-pure)/es|stable|actual|full/iterator/drop
core-js(-pure)/es|stable|actual|full/iterator/every
core-js(-pure)/es|stable|actual|full/iterator/filter
core-js(-pure)/es|stable|actual|full/iterator/find
core-js(-pure)/es|stable|actual|full/iterator/flat-map
core-js(-pure)/es|stable|actual|full/iterator/for-each
core-js(-pure)/es|stable|actual|full/iterator/from
core-js(-pure)/es|stable|actual|full/iterator/map
core-js(-pure)/es|stable|actual|full/iterator/reduce
core-js(-pure)/es|stable|actual|full/iterator/some
core-js(-pure)/es|stable|actual|full/iterator/take
core-js(-pure)/es|stable|actual|full/iterator/to-array
core-js(-pure)/es|stable|actual|full/iterator/zip
core-js(-pure)/es|stable|actual|full/iterator/zip-keyed

[1, 2, 3, 4, 5, 6, 7].values()
  .drop(1)
  .take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

Iterator.from({
  next: () => ({ done: Math.random() > 0.9, value: Math.random() * 10 | 0 }),
}).toArray(); // => [7, 6, 3, 0, 2, 8]

Iterator.concat([0, 1].values(), [2, 3], function * () {
  yield 4;
  yield 5;
}()).toArray(); // => [0, 1, 2, 3, 4, 5]

Iterator.zip([
  [0, 1, 2],
  [3, 4, 5],
]).toArray();  // => [[0, 3], [1, 4], [2, 5]]

Iterator.zipKeyed({
  a: [0, 1, 2],
  b: [3, 4, 5, 6],
  c: [7, 8, 9],
}, {
  mode: 'longest',
  padding: { c: 10 },
}).toArray(); // =>
/*
[
  { a: 0,         b: 3, c: 7  },
  { a: 1,         b: 4, c: 8  },
  { a: 2,         b: 5, c: 9  },
  { a: undefined, b: 6, c: 10 },
];
 */

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console.log(RegExp.escape('10$')); // => '\\x310\\$'
console.log(RegExp.escape('abcdefg_123456')); // => '\\x61bcdefg_123456'
console.log(RegExp.escape('Привет')); // => 'Привет'
console.log(RegExp.escape('(){}[]|,.?*+-^$=<>\\/#&!%:;@~\'"`'));
// => '\\(\\)\\{\\}\\[\\]\\|\\x2c\\.\\?\\*\\+\\x2d\\^\\$\\x3d\\x3c\\x3e\\\\\\/\\x23\\x26\\x21\\x25\\x3a\\x3b\\x40\\x7e\\x27\\x22\\x60'
console.log(RegExp.escape('\u0009\u000A\u000B\u000C\u000D\u0020\u00A0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u202F\u205F\u3000\u2028\u2029\uFEFF'));
// => '\\\t\\\n\\\v\\\f\\\r\\x20\\xa0\\u1680\\u2000\\u2001\\u2002\\u2003\\u2004\\u2005\\u2006\\u2007\\u2008\\u2009\\u200a\\u202f\\u205f\\u3000\\u2028\\u2029\\ufeff'
console.log(RegExp.escape('💩')); // => '💩'
console.log(RegExp.escape('\uD83D')); // => '\\ud83d'

Number('0b1010101'); // => 85
Number('0o7654321'); // => 2054353

class Number {
  constructor(value: any): number;
  toExponential(digits: number): string;
  toFixed(digits: number): string;
  toPrecision(precision: number): string;
  static isFinite(number: any): boolean;
  static isNaN(number: any): boolean;
  static isInteger(number: any): boolean;
  static isSafeInteger(number: any): boolean;
  static parseFloat(string: string): number;
  static parseInt(string: string, radix?: number = 10): number;
  static EPSILON: number;
  static MAX_SAFE_INTEGER: number;
  static MIN_SAFE_INTEGER: number;
}

function parseFloat(string: string): number;
function parseInt(string: string, radix?: number = 10): number;

core-js(-pure)/es|stable|actual|full/number
core-js(-pure)/es|stable|actual|full/number/constructor
core-js(-pure)/es|stable|actual|full/number/is-finite
core-js(-pure)/es|stable|actual|full/number/is-nan
core-js(-pure)/es|stable|actual|full/number/is-integer
core-js(-pure)/es|stable|actual|full/number/is-safe-integer
core-js(-pure)/es|stable|actual|full/number/parse-float
core-js(-pure)/es|stable|actual|full/number/parse-int
core-js(-pure)/es|stable|actual|full/number/epsilon
core-js(-pure)/es|stable|actual|full/number/max-safe-integer
core-js(-pure)/es|stable|actual|full/number/min-safe-integer
core-js(-pure)/es|stable|actual|full/number(/virtual)/to-exponential
core-js(-pure)/es|stable|actual|full/number(/virtual)/to-fixed
core-js(-pure)/es|stable|actual|full/number(/virtual)/to-precision
core-js(-pure)/es|stable|actual|full/parse-float
core-js(-pure)/es|stable|actual|full/parse-int

namespace Math {
  acosh(number: number): number;
  asinh(number: number): number;
  atanh(number: number): number;
  cbrt(number: number): number;
  clz32(number: number): number;
  cosh(number: number): number;
  expm1(number: number): number;
  fround(number: number): number;
  f16round(number: any): number;
  hypot(...args: Array<number>): number;
  imul(number1: number, number2: number): number;
  log1p(number: number): number;
  log10(number: number): number;
  log2(number: number): number;
  sign(number: number): 1 | -1 | 0 | -0 | NaN;
  sinh(number: number): number;
  sumPrecise(items: Iterable<number>): Number;
  tanh(number: number): number;
  trunc(number: number): number;
}

core-js(-pure)/es|stable|actual|full/math
core-js(-pure)/es|stable|actual|full/math/acosh
core-js(-pure)/es|stable|actual|full/math/asinh
core-js(-pure)/es|stable|actual|full/math/atanh
core-js(-pure)/es|stable|actual|full/math/cbrt
core-js(-pure)/es|stable|actual|full/math/clz32
core-js(-pure)/es|stable|actual|full/math/cosh
core-js(-pure)/es|stable|actual|full/math/expm1
core-js(-pure)/es|stable|actual|full/math/fround
core-js(-pure)/es|stable|actual|full/math/f16round
core-js(-pure)/es|stable|actual|full/math/hypot
core-js(-pure)/es|stable|actual|full/math/imul
core-js(-pure)/es|stable|actual|full/math/log1p
core-js(-pure)/es|stable|actual|full/math/log10
core-js(-pure)/es|stable|actual|full/math/log2
core-js(-pure)/es|stable|actual|full/math/sign
core-js(-pure)/es|stable|actual|full/math/sinh
core-js(-pure)/es|stable|actual|full/math/sum-precise
core-js(-pure)/es|stable|actual|full/math/tanh
core-js(-pure)/es|stable|actual|full/math/trunc

1e20 + 0.1 + -1e20; // => 0
Math.sumPrecise([1e20, 0.1, -1e20]); // => 0.1

class Date {
  getYear(): int;
  setYear(year: int): number;
  toGMTString(): string;
  toISOString(): string;
  toJSON(): string;
  toString(): string;
  @@toPrimitive(hint: 'default' | 'number' | 'string'): string | number;
  static now(): number;
}

core-js/es|stable|actual|full/date
core-js/es|stable|actual|full/date/to-string
core-js(-pure)/es|stable|actual|full/date/now
core-js(-pure)/es|stable|actual|full/date/get-year
core-js(-pure)/es|stable|actual|full/date/set-year
core-js(-pure)/es|stable|actual|full/date/to-gmt-string
core-js(-pure)/es|stable|actual|full/date/to-iso-string
core-js(-pure)/es|stable|actual|full/date/to-json
core-js(-pure)/es|stable|actual|full/date/to-primitive

new Date(NaN).toString(); // => 'Invalid Date'

class Promise {
  constructor(executor: (resolve: Function, reject: Function) => void): Promise;
  then(onFulfilled: Function, onRejected: Function): Promise;
  catch(onRejected: Function): Promise;
  finally(onFinally: Function): Promise;
  static all(iterable: Iterable): Promise;
  static allSettled(iterable: Iterable): Promise;
  static any(promises: Iterable): Promise;
  static race(iterable: Iterable): Promise;
  static reject(r: any): Promise;
  static resolve(x: any): Promise;
  static try(callbackfn: Function, ...args?: Array<mixed>): Promise;
  static withResolvers(): { promise: Promise, resolve: function, reject: function };
}

core-js(-pure)/es|stable|actual|full/promise
core-js(-pure)/es|stable|actual|full/promise/all-settled
core-js(-pure)/es|stable|actual|full/promise/any
core-js(-pure)/es|stable|actual|full/promise/finally
core-js(-pure)/es|stable|actual|full/promise/try
core-js(-pure)/es|stable|actual|full/promise/with-resolvers

/* eslint-disable promise/prefer-await-to-callbacks -- example */
function sleepRandom(time) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, time * 1e3, 0 | Math.random() * 1e3);
  });
}

console.log('Run');                    // => Run
sleepRandom(5).then(result => {
  console.log(result);                 // => 869, after 5 sec.
  return sleepRandom(10);
}).then(result => {
  console.log(result);                 // => 202, after 10 sec.
}).then(() => {
  console.log('immediately after');    // => immediately after
  throw new Error('Irror!');
}).then(() => {
  console.log('will not be displayed');
}).catch(error => console.log(error)); // => => Error: Irror!

/* eslint-disable promise/prefer-await-to-callbacks -- example */
Promise.resolve(42).then(x => console.log(x));         // => 42
Promise.reject(42).catch(error => console.log(error)); // => 42

Promise.resolve($.getJSON('/data.json')); // => ES promise

Promise.resolve(42).finally(() => console.log('You will see it anyway'));

Promise.reject(42).finally(() => console.log('You will see it anyway'));

Promise.all([
  'foo',
  sleepRandom(5),
  sleepRandom(15),
  sleepRandom(10),            // after 15 sec:
]).then(x => console.log(x)); // => ['foo', 956, 85, 382]

/* eslint-disable promise/prefer-await-to-callbacks -- example */
function timeLimit(promise, time) {
  return Promise.race([promise, new Promise((resolve, reject) => {
    setTimeout(reject, time * 1e3, new Error(`Await > ${ time } sec`));
  })]);
}

timeLimit(sleepRandom(5), 10).then(x => console.log(x));           // => 853, after 5 sec.
timeLimit(sleepRandom(15), 10).catch(error => console.log(error)); // Error: Await > 10 sec

Promise.allSettled([
  Promise.resolve(1),
  Promise.reject(2),
  Promise.resolve(3),
]).then(console.log); // => [{ value: 1, status: 'fulfilled' }, { reason: 2, status: 'rejected' }, { value: 3, status: 'fulfilled' }]

Promise.any([
  Promise.resolve(1),
  Promise.reject(2),
  Promise.resolve(3),
]).then(console.log); // => 1

Promise.any([
  Promise.reject(1),
  Promise.reject(2),
  Promise.reject(3),
]).catch(({ errors }) => console.log(errors)); // => [1, 2, 3]

/* eslint-disable promise/prefer-await-to-callbacks -- example */
Promise.try(() => 42).then(it => console.log(`Promise, resolved as ${ it }`));

Promise.try(() => { throw new Error('42'); }).catch(error => console.log(`Promise, rejected as ${ error }`));

Promise.try(async () => 42).then(it => console.log(`Promise, resolved as ${ it }`));

Promise.try(async () => { throw new Error('42'); }).catch(error => console.log(`Promise, rejected as ${ error }`));

Promise.try(it => it, 42).then(it => console.log(`Promise, resolved as ${ it }`));

const d = Promise.withResolvers();
d.resolve(42);
d.promise.then(console.log); // => 42

let delay = time => new Promise(resolve => setTimeout(resolve, time));

async function sleepRandom(time) {
  await delay(time * 1e3);
  return 0 | Math.random() * 1e3;
}

async function sleepError(time, msg) {
  await delay(time * 1e3);
  throw new Error(msg);
}

(async () => {
  try {
    console.log('Run');                // => Run
    console.log(await sleepRandom(5)); // => 936, after 5 sec.
    let [a, b, c] = await Promise.all([
      sleepRandom(5),
      sleepRandom(15),
      sleepRandom(10),
    ]);
    console.log(a, b, c);              // => 210 445 71, after 15 sec.
    await sleepError(5, 'Error!');
    console.log('Will not be displayed');
  } catch (error) {
    console.log(error);                // => Error: 'Error!', after 5 sec.
  }
})();

process.on('unhandledRejection', (reason, promise) => console.log('unhandled', reason, promise));
process.on('rejectionHandled', promise => console.log('handled', promise));

let promise = Promise.reject(42);
// unhandled 42 [object Promise]

// eslint-disable-next-line promise/prefer-await-to-then -- example
setTimeout(() => promise.catch(() => { /* empty */ }), 1e3);
// handled [object Promise]

globalThis.addEventListener('unhandledrejection', e => console.log('unhandled', e.reason, e.promise));
globalThis.addEventListener('rejectionhandled', e => console.log('handled', e.reason, e.promise));
// or
globalThis.onunhandledrejection = e => console.log('unhandled', e.reason, e.promise);
globalThis.onrejectionhandled = e => console.log('handled', e.reason, e.promise);

let promise = Promise.reject(42);
// => unhandled 42 [object Promise]

// eslint-disable-next-line promise/prefer-await-to-then -- example
setTimeout(() => promise.catch(() => { /* empty */ }), 1e3);
// => handled 42 [object Promise]

class Symbol {
  constructor(description?): symbol;
  readonly attribute description: string | void;
  static asyncDispose: @@asyncDispose;
  static asyncIterator: @@asyncIterator;
  static dispose: @@dispose;
  static hasInstance: @@hasInstance;
  static isConcatSpreadable: @@isConcatSpreadable;
  static iterator: @@iterator;
  static match: @@match;
  static replace: @@replace;
  static search: @@search;
  static species: @@species;
  static split: @@split;
  static toPrimitive: @@toPrimitive;
  static toStringTag: @@toStringTag;
  static unscopables: @@unscopables;
  static for(key: string): symbol;
  static keyFor(sym: symbol): string;
  static useSimple(): void;
  static useSetter(): void;
}

class Object {
  static getOwnPropertySymbols(object: any): Array<symbol>;
}

class Object {
  static create(prototype: Object | null, properties?: { [property: PropertyKey]: PropertyDescriptor }): Object;
  static defineProperties(object: Object, properties: { [property: PropertyKey]: PropertyDescriptor })): Object;
  static defineProperty(object: Object, property: PropertyKey, attributes: PropertyDescriptor): Object;
  static getOwnPropertyDescriptor(object: any, property: PropertyKey): PropertyDescriptor | void;
  static getOwnPropertyNames(object: any): Array<string>;
  propertyIsEnumerable(key: PropertyKey): boolean;
}

core-js(-pure)/es|stable|actual|full/symbol
core-js(-pure)/es|stable|actual|full/symbol/async-dispose
core-js(-pure)/es|stable|actual|full/symbol/async-iterator
core-js/es|stable|actual|full/symbol/description
core-js(-pure)/es|stable|actual|full/symbol/dispose
core-js(-pure)/es|stable|actual|full/symbol/has-instance
core-js(-pure)/es|stable|actual|full/symbol/is-concat-spreadable
core-js(-pure)/es|stable|actual|full/symbol/iterator
core-js(-pure)/es|stable|actual|full/symbol/match
core-js(-pure)/es|stable|actual|full/symbol/replace
core-js(-pure)/es|stable|actual|full/symbol/search
core-js(-pure)/es|stable|actual|full/symbol/species
core-js(-pure)/es|stable|actual|full/symbol/split
core-js(-pure)/es|stable|actual|full/symbol/to-primitive
core-js(-pure)/es|stable|actual|full/symbol/to-string-tag
core-js(-pure)/es|stable|actual|full/symbol/unscopables
core-js(-pure)/es|stable|actual|full/symbol/for
core-js(-pure)/es|stable|actual|full/symbol/key-for
core-js(-pure)/es|stable|actual|full/object/get-own-property-symbols
core-js(-pure)/es|stable|actual|full/math/to-string-tag

let Person = (() => {
  let NAME = Symbol('name');
  return class {
    constructor(name) {
      this[NAME] = name;
    }
    getName() {
      return this[NAME];
    }
  };
})();

let person = new Person('Vasya');
console.log(person.getName());            // => 'Vasya'
console.log(person.name);                 // => undefined
console.log(person[Symbol('name')]);      // => undefined, symbols are uniq
for (let key in person) console.log(key); // => nothing, symbols are not enumerable

let symbol = Symbol.for('key');
symbol === Symbol.for('key'); // true
Symbol.keyFor(symbol);        // 'key'

let object = { a: 1 };
Object.defineProperty(object, 'b', { value: 2 });
object[Symbol('c')] = 3;
Object.keys(object);                  // => ['a']
Object.getOwnPropertyNames(object);   // => ['a', 'b']
Object.getOwnPropertySymbols(object); // => [Symbol(c)]
Reflect.ownKeys(object);              // => ['a', 'b', Symbol(c)]

Symbol('foo').description; // => 'foo'
// eslint-disable-next-line symbol-description -- example
Symbol().description;      // => undefined

Symbol.useSimple();
let object1 = { [Symbol('symbol1')]: true };
for (let key in object1) console.log(key); // => 'Symbol(symbol1)_t.qamkg9f3q', w/o native Symbol

Symbol.useSetter();
let object2 = { [Symbol('symbol2')]: true };
for (let key in object2) console.log(key); // nothing

class Map {
  constructor(iterable?: Iterable<[key, value]>): Map;
  clear(): void;
  delete(key: any): boolean;
  forEach(callbackfn: (value: any, key: any, target: any) => void, thisArg: any): void;
  get(key: any): any;
  getOrInsert(key: any, value: any): any;
  getOrInsertComputed(key: any, (key: any) => value: any): any;
  has(key: any): boolean;
  set(key: any, val: any): this;
  values(): Iterator<value>;
  keys(): Iterator<key>;
  entries(): Iterator<[key, value]>;
  @@iterator(): Iterator<[key, value]>;
  readonly attribute size: number;
  static groupBy(items: Iterable, callbackfn: (value: any, index: number) => key): Map<key, Array<mixed>>;
}

core-js(-pure)/es|stable|actual|full/map
core-js(-pure)/es|stable|actual|full/map/group-by
core-js(-pure)/es|stable|actual|full/map/get-or-insert
core-js(-pure)/es|stable|actual|full/map/get-or-insert-computed

let array = [1];

let map = new Map([['a', 1], [42, 2]]);
map.set(array, 3).set(true, 4);

console.log(map.size);        // => 4
console.log(map.has(array));  // => true
console.log(map.has([1]));    // => false
console.log(map.get(array));  // => 3
map.forEach((val, key) => {
  console.log(val);           // => 1, 2, 3, 4
  console.log(key);           // => 'a', 42, [1], true
});
map.delete(array);
console.log(map.size);        // => 3
console.log(map.get(array));  // => undefined
console.log(Array.from(map)); // => [['a', 1], [42, 2], [true, 4]]

map = new Map([['a', 1], ['b', 2], ['c', 3]]);

for (let [key, value] of map) {
  console.log(key);                                 // => 'a', 'b', 'c'
  console.log(value);                               // => 1, 2, 3
}
for (let value of map.values()) console.log(value); // => 1, 2, 3
for (let key of map.keys()) console.log(key);       // => 'a', 'b', 'c'
for (let [key, value] of map.entries()) {
  console.log(key);                                 // => 'a', 'b', 'c'
  console.log(value);                               // => 1, 2, 3
}

map = Map.groupBy([1, 2, 3, 4, 5], it => it % 2);
map.get(1); // => [1, 3, 5]
map.get(0); // => [2, 4]

map = new Map([['a', 1]]);

map.getOrInsert('a', 2); // => 1

map.getOrInsert('b', 3); // => 3

map.getOrInsertComputed('a', key => key); // => 1

map.getOrInsertComputed('c', key => key); // => 'c'

console.log(map); // => Map { 'a': 1, 'b': 3, 'c': 'c' }

class Set {
  constructor(iterable?: Iterable<value>): Set;
  add(key: any): this;
  clear(): void;
  delete(key: any): boolean;
  forEach((value: any, key: any, target: any) => void, thisArg: any): void;
  has(key: any): boolean;
  values(): Iterator<value>;
  keys(): Iterator<value>;
  entries(): Iterator<[value, value]>;
  difference(other: SetLike<mixed>): Set;
  intersection(other: SetLike<mixed>): Set;
  isDisjointFrom(other: SetLike<mixed>): boolean;
  isSubsetOf(other: SetLike<mixed>): boolean;
  isSupersetOf(other: SetLike<mixed>): boolean;
  symmetricDifference(other: SetLike<mixed>): Set;
  union(other: SetLike<mixed>): Set;
  @@iterator(): Iterator<value>;
  readonly attribute size: number;
}

core-js(-pure)/es|stable|actual|full/set
core-js(-pure)/es|stable|actual|full/set/difference
core-js(-pure)/es|stable|actual|full/set/intersection
core-js(-pure)/es|stable|actual|full/set/is-disjoint-from
core-js(-pure)/es|stable|actual|full/set/is-subset-of
core-js(-pure)/es|stable|actual|full/set/is-superset-of
core-js(-pure)/es|stable|actual|full/set/symmetric-difference
core-js(-pure)/es|stable|actual|full/set/union

let set = new Set(['a', 'b', 'a', 'c']);
set.add('d').add('b').add('e');
console.log(set.size);        // => 5
console.log(set.has('b'));    // => true
set.forEach(it => {
  console.log(it);            // => 'a', 'b', 'c', 'd', 'e'
});
set.delete('b');
console.log(set.size);        // => 4
console.log(set.has('b'));    // => false
console.log(Array.from(set)); // => ['a', 'c', 'd', 'e']

set = new Set([1, 2, 3, 2, 1]);

for (let value of set) console.log(value);          // => 1, 2, 3
for (let value of set.values()) console.log(value); // => 1, 2, 3
for (let key of set.keys()) console.log(key);       // => 1, 2, 3
for (let [key, value] of set.entries()) {
  console.log(key);                                 // => 1, 2, 3
  console.log(value);                               // => 1, 2, 3
}

new Set([1, 2, 3]).union(new Set([3, 4, 5]));               // => Set {1, 2, 3, 4, 5}
new Set([1, 2, 3]).intersection(new Set([3, 4, 5]));        // => Set {3}
new Set([1, 2, 3]).difference(new Set([3, 4, 5]));          // => Set {1, 2}
new Set([1, 2, 3]).symmetricDifference(new Set([3, 4, 5])); // => Set {1, 2, 4, 5}
new Set([1, 2, 3]).isDisjointFrom(new Set([4, 5, 6]));      // => true
new Set([1, 2, 3]).isSubsetOf(new Set([5, 4, 3, 2, 1]));    // => true
new Set([5, 4, 3, 2, 1]).isSupersetOf(new Set([1, 2, 3]));  // => true

class WeakMap {
  constructor(iterable?: Iterable<[key, value]>): WeakMap;
  delete(key: object | symbol): boolean;
  get(key: object | symbol): any;
  getOrInsert(key: object | symbol, value: any): any;
  getOrInsertComputed(key: object | symbol, (key: any) => value: any): any;
  has(key: object | symbol): boolean;
  set(key: object | symbol, val: any): this;
}

core-js(-pure)/es|stable|actual|full/weak-map
core-js(-pure)/es|stable|actual|full/weak-map/get-or-insert
core-js(-pure)/es|stable|actual|full/weak-map/get-or-insert-computed

let a = [1];
let b = [2];
let c = [3];

let weakmap = new WeakMap([[a, 1], [b, 2]]);
weakmap.set(c, 3).set(b, 4);
console.log(weakmap.has(a));   // => true
console.log(weakmap.has([1])); // => false
console.log(weakmap.get(a));   // => 1
weakmap.delete(a);
console.log(weakmap.get(a));   // => undefined

// Private properties store:
let Person = (() => {
  let names = new WeakMap();
  return class {
    constructor(name) {
      names.set(this, name);
    }
    getName() {
      return names.get(this);
    }
  };
})();

let person = new Person('Vasya');
console.log(person.getName());            // => 'Vasya'
for (let key in person) console.log(key); // => only 'getName'

class WeakSet {
  constructor(iterable?: Iterable<value>): WeakSet;
  add(key: object | symbol): this;
  delete(key: object | symbol): boolean;
  has(key: object | symbol): boolean;
}

core-js(-pure)/es|stable|actual|full/weak-set

let a = [1];
let b = [2];
let c = [3];

let weakset = new WeakSet([a, b, a]);
weakset.add(c).add(b).add(c);
console.log(weakset.has(b));   // => true
console.log(weakset.has([2])); // => false
weakset.delete(b);
console.log(weakset.has(b));   // => false

class Symbol {
  static asyncDispose: @@asyncDispose;
  static dispose: @@dispose;
}

class DisposableStack {
  constructor(): DisposableStack;
  dispose(): undefined;
  use(value: Disposable): value;
  adopt(value: object, onDispose: Function): value;
  defer(onDispose: Function): undefined;
  move(): DisposableStack;
  @@dispose(): undefined;
  @@toStringTag: 'DisposableStack';
}

class AsyncDisposableStack {
  constructor(): AsyncDisposableStack;
  disposeAsync(): Promise;
  use(value: AsyncDisposable | Disposable): value;
  adopt(value: object, onDispose: Function): value;
  defer(onDispose: Function): undefined;
  move(): AsyncDisposableStack;
  @@asyncDispose(): Promise;
  @@toStringTag: 'AsyncDisposableStack';
}

class SuppressedError extends Error {
  constructor(error: any, suppressed: any, message?: string): SuppressedError;
  error: any;
  suppressed: any;
  message: string;
  cause: any;
}

class Iterator {
  @@dispose(): undefined;
}

class AsyncIterator {
  @@asyncDispose(): Promise;
}

core-js(-pure)/es|stable|actual|full/disposable-stack
core-js(-pure)/es|stable|actual|full/async-disposable-stack
core-js(-pure)/es|stable|actual|full/iterator/dispose
core-js(-pure)/es|stable|actual|full/async-iterator/async-dispose

/* Detailed source-code truncated for AI context efficiency. */

/* Detailed source-code truncated for AI context efficiency. */

new Int32Array(4);                          // => [0, 0, 0, 0]
new Uint8ClampedArray([1, 2, 3, 666]);      // => [1, 2, 3, 255]
new Float32Array(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3]

let buffer = new ArrayBuffer(8);
let view = new DataView(buffer);
view.setFloat64(0, 123.456, true);
new Uint8Array(buffer.slice(4)); // => [47, 221, 94, 64]

Int8Array.of(1, 1.5, 5.7, 745);      // => [1, 1, 5, -23]
Uint8Array.from([1, 1.5, 5.7, 745]); // => [1, 1, 5, 233]

let typed = new Uint8Array([1, 2, 3]);

let a = typed.slice(1);    // => [2, 3]
typed.buffer === a.buffer; // => false
let b = typed.subarray(1); // => [2, 3]
typed.buffer === b.buffer; // => true

typed.filter(it => it % 2); // => [1, 3]
typed.map(it => it * 1.5);  // => [1, 3, 4]

for (let value of typed) console.log(value);          // => 1, 2, 3
for (let value of typed.values()) console.log(value); // => 1, 2, 3
for (let key of typed.keys()) console.log(key);       // => 0, 1, 2
for (let [key, value] of typed.entries()) {
  console.log(key);                                   // => 0, 1, 2
  console.log(value);                                 // => 1, 2, 3
}

new Int32Array([1, 2, 3]).at(1);  // => 2
new Int32Array([1, 2, 3]).at(-1); // => 3

buffer = Int8Array.of(1, 2, 3, 4, 5, 6, 7, 8).buffer;
console.log(buffer.byteLength); // => 8
console.log(buffer.detached); // => false
const newBuffer = buffer.transfer(4);
console.log(buffer.byteLength); // => 0
console.log(buffer.detached); // => true
console.log(newBuffer.byteLength); // => 4
console.log(newBuffer.detached); // => false
console.log([...new Int8Array(newBuffer)]); // => [1, 2, 3, 4]

let arr = new Uint8Array([72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100]);
console.log(arr.toBase64()); // => 'SGVsbG8gV29ybGQ='
console.log(arr.toBase64({ omitPadding: true })); // => 'SGVsbG8gV29ybGQ'
console.log(arr.toHex()); // => '48656c6c6f20576f726c64'
console.log(Uint8Array.fromBase64('SGVsbG8gV29ybGQ=')); // => Uint8Array([72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100])
console.log(Uint8Array.fromHex('48656c6c6f20576f726c64')); // => Uint8Array([72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100])

namespace Reflect {
  apply(target: Function, thisArgument: any, argumentsList: Array<mixed>): any;
  construct(target: Function, argumentsList: Array<mixed>, newTarget?: Function): Object;
  defineProperty(target: Object, propertyKey: PropertyKey, attributes: PropertyDescriptor): boolean;
  deleteProperty(target: Object, propertyKey: PropertyKey): boolean;
  get(target: Object, propertyKey: PropertyKey, receiver?: any): any;
  getOwnPropertyDescriptor(target: Object, propertyKey: PropertyKey): PropertyDescriptor | void;
  getPrototypeOf(target: Object): Object | null;
  has(target: Object, propertyKey: PropertyKey): boolean;
  isExtensible(target: Object): boolean;
  ownKeys(target: Object): Array<string | symbol>;
  preventExtensions(target: Object): boolean;
  set(target: Object, propertyKey: PropertyKey, V: any, receiver?: any): boolean;
  setPrototypeOf(target: Object, proto: Object | null): boolean; // required __proto__ - IE11+
}

core-js(-pure)/es|stable|actual|full/reflect
core-js(-pure)/es|stable|actual|full/reflect/apply
core-js(-pure)/es|stable|actual|full/reflect/construct
core-js(-pure)/es|stable|actual|full/reflect/define-property
core-js(-pure)/es|stable|actual|full/reflect/delete-property
core-js(-pure)/es|stable|actual|full/reflect/get
core-js(-pure)/es|stable|actual|full/reflect/get-own-property-descriptor
core-js(-pure)/es|stable|actual|full/reflect/get-prototype-of
core-js(-pure)/es|stable|actual|full/reflect/has
core-js(-pure)/es|stable|actual|full/reflect/is-extensible
core-js(-pure)/es|stable|actual|full/reflect/own-keys
core-js(-pure)/es|stable|actual|full/reflect/prevent-extensions
core-js(-pure)/es|stable|actual|full/reflect/set
core-js(-pure)/es|stable|actual|full/reflect/set-prototype-of

let object = { a: 1 };
Object.defineProperty(object, 'b', { value: 2 });
object[Symbol('c')] = 3;
Reflect.ownKeys(object); // => ['a', 'b', Symbol(c)]

function C(a, b) {
  this.c = a + b;
}

let instance = Reflect.construct(C, [20, 22]);
instance.c; // => 42

namespace JSON {
  isRawJSON(O: any): boolean;
  parse(text: string, reviver?: (this: any, key: string, value: any, context: { source?: string }) => any): any;
  rawJSON(text: any): RawJSON;
  stringify(value: any, replacer?: Array<string | number> | (this: any, key: string, value: any) => any, space?: string | number): string | void;
  @@toStringTag: 'JSON';
}

core-js(-pure)/es|stable|actual|full/json/is-raw-json
core-js(-pure)/es|stable|actual|full/json/parse
core-js(-pure)/es|stable|actual|full/json/raw-json
core-js(-pure)/es|stable|actual|full/json/stringify
core-js(-pure)/es|stable|actual|full/json/stringify
core-js(-pure)/es|stable|actual|full/json/to-string-tag

JSON.stringify({ '𠮷': ['\uDF06\uD834'] }); // => '{"𠮷":["\\udf06\\ud834"]}'

function digitsToBigInt(key, val, { source }) {
  return /^\d+$/.test(source) ? BigInt(source) : val;
}

function bigIntToRawJSON(key, val) {
  return typeof val === 'bigint' ? JSON.rawJSON(String(val)) : val;
}

const tooBigForNumber = BigInt(Number.MAX_SAFE_INTEGER) + 2n;
JSON.parse(String(tooBigForNumber), digitsToBigInt) === tooBigForNumber; // true

const wayTooBig = BigInt(`1${ '0'.repeat(1000) }`);
JSON.parse(String(wayTooBig), digitsToBigInt) === wayTooBig; // true

const embedded = JSON.stringify({ tooBigForNumber }, bigIntToRawJSON);
embedded === '{"tooBigForNumber":9007199254740993}'; // true

let globalThis: GlobalThisValue;

core-js(-pure)/es|stable|actual|full/global-this

globalThis.Array === Array; // => true

let globalThis: GlobalThisValue;

core-js/proposals/global-this

class Array {
  at(index: int): any;
}

class String {
  at(index: int): string;
}

class %TypedArray% {
  at(index: int): number;
}

core-js/proposals/relative-indexing-method

class Array {
  includes(searchElement: any, from?: number): boolean;
}

class %TypedArray% {
  includes(searchElement: any, from?: number): boolean;
}

core-js/proposals/array-includes

class Array {
  flat(depthArg?: number = 1): Array<mixed>;
  flatMap(mapFn: (value: any, index: number, target: any) => any, thisArg: any): Array<mixed>;
}

core-js/proposals/array-flat-map

class Array {
  findLast(callbackfn: (value: any, index: number, target: any) => boolean, thisArg?: any): any;
  findLastIndex(callbackfn: (value: any, index: number, target: any) => boolean, thisArg?: any): uint;
}

class %TypedArray% {
  findLast(callbackfn: (value: any, index: number, target: %TypedArray%) => boolean, thisArg?: any): any;
  findLastIndex(callbackfn: (value: any, index: number, target: %TypedArray%) => boolean, thisArg?: any): uint;
}

core-js/proposals/array-find-from-last

class Array {
  toReversed(): Array<mixed>;
  toSpliced(start?: number, deleteCount?: number, ...items: Array<mixed>): Array<mixed>;
  toSorted(comparefn?: (a: any, b: any) => number): Array<mixed>;
  with(index: includes, value: any): Array<mixed>;
}

class %TypedArray% {
  toReversed(): %TypedArray%;
  toSorted(comparefn?: (a: any, b: any) => number): %TypedArray%;
  with(index: includes, value: any): %TypedArray%;
}

core-js/proposals/change-array-by-copy-stage-4
core-js(-pure)/es|stable|actual|full/array(/virtual)/to-reversed
core-js(-pure)/es|stable|actual|full/array(/virtual)/to-sorted
core-js(-pure)/es|stable|actual|full/array(/virtual)/to-spliced
core-js(-pure)/es|stable|actual|full/array(/virtual)/with
core-js/es|stable|actual|full/typed-array/to-reversed
core-js/es|stable|actual|full/typed-array/to-sorted
core-js/es|stable|actual|full/typed-array/with

class Object {
  static groupBy(items: Iterable, callbackfn: (value: any, index: number) => key): { [key]: Array<mixed> };
}

class Map {
  static groupBy(items: Iterable, callbackfn: (value: any, index: number) => key): Map<key, Array<mixed>>;
}

core-js/proposals/array-grouping-v2

class Array {
  static fromAsync(asyncItems: AsyncIterable | Iterable | ArrayLike, mapfn?: (value: any, index: number) => any, thisArg?: any): Array;
}

core-js/proposals/array-from-async-stage-2

class ArrayBuffer {
  readonly attribute detached: boolean;
  transfer(newLength?: number): ArrayBuffer;
  transferToFixedLength(newLength?: number): ArrayBuffer;
}

core-js/proposals/array-buffer-transfer

class Uint8Array {
  static fromBase64(string: string, options?: { alphabet?: 'base64' | 'base64url', lastChunkHandling?: 'loose' | 'strict' | 'stop-before-partial' }): Uint8Array;
  static fromHex(string: string): Uint8Array;
  setFromBase64(string: string, options?: { alphabet?: 'base64' | 'base64url', lastChunkHandling?: 'loose' | 'strict' | 'stop-before-partial' }): { read: uint, written: uint };
  setFromHex(string: string): { read: uint, written: uint };
  toBase64(options?: { alphabet?: 'base64' | 'base64url', omitPadding?: boolean }): string;
  toHex(): string;
}

core-js/proposals/array-buffer-base64

class Error {
  static isError(value: any): boolean;
}

core-js/proposals/is-error

class Symbol {
  static asyncDispose: @@asyncDispose;
  static dispose: @@dispose;
}

class DisposableStack {
  constructor(): DisposableStack;
  dispose(): undefined;
  use(value: Disposable): value;
  adopt(value: object, onDispose: Function): value;
  defer(onDispose: Function): undefined;
  move(): DisposableStack;
  @@dispose(): undefined;
  @@toStringTag: 'DisposableStack';
}

class AsyncDisposableStack {
  constructor(): AsyncDisposableStack;
  disposeAsync(): Promise;
  use(value: AsyncDisposable | Disposable): value;
  adopt(value: object, onDispose: Function): value;
  defer(onDispose: Function): undefined;
  move(): AsyncDisposableStack;
  @@asyncDispose(): Promise;
  @@toStringTag: 'AsyncDisposableStack';
}

class SuppressedError extends Error {
  constructor(error: any, suppressed: any, message?: string): SuppressedError;
  error: any;
  suppressed: any;
  message: string;
  cause: any;
}

class Iterator {
  @@dispose(): undefined;
}

class AsyncIterator {
  @@asyncDispose(): Promise;
}

core-js/proposals/explicit-resource-management

class DataView {
  getFloat16(offset: any, littleEndian?: boolean = false): float16
  setFloat16(offset: any, value: any, littleEndian?: boolean = false): void;
}

namespace Math {
  fround(number: any): number;
}

core-js/proposals/float16

class Iterator {
  static from(iterable: Iterable<any> | Iterator<any>): Iterator<any>;
  drop(limit: uint): Iterator<any>;
  every(callbackfn: (value: any, counter: uint) => boolean): boolean;
  filter(callbackfn: (value: any, counter: uint) => boolean): Iterator<any>;
  find(callbackfn: (value: any, counter: uint) => boolean)): any;
  flatMap(callbackfn: (value: any, counter: uint) => Iterable<any> | Iterator<any>): Iterator<any>;
  forEach(callbackfn: (value: any, counter: uint) => void): void;
  map(callbackfn: (value: any, counter: uint) => any): Iterator<any>;
  reduce(callbackfn: (memo: any, value: any, counter: uint) => any, initialValue: any): any;
  some(callbackfn: (value: any, counter: uint) => boolean): boolean;
  take(limit: uint): Iterator<any>;
  toArray(): Array<any>;
  @@toStringTag: 'Iterator'
}

core-js/proposals/iterator-helpers-stage-3-2

class Iterator {
  static concat(...items: Array): Iterator<any>;
}

core-js/proposals/iterator-sequencing

class Iterator {
  zip<T extends readonly Iterable[]>(
    iterables: T,
    options?: {
      mode?: 'shortest' | 'longest' | 'strict';
      padding?: { [K in keyof T]?: T[K] extends Iterable ? U : never };
    }
  ): IterableIterator<{ [K in keyof T]: T[K] extends Iterable ? U : never }>;
  zipKeyed<K extends PropertyKey, V extends Record<K, Iterable>>(
    iterables: V,
    options?: {
      mode?: 'shortest' | 'longest' | 'strict';
      padding?: { [P in keyof V]?: V[P] extends Iterable ? U : never };
    }
  ): IterableIterator<{ [P in keyof V]: V[P] extends Iterable ? U : never }>;
}

core-js/proposals/joint-iteration
core-js(-pure)/es|stable|actual|full/iterator/zip
core-js(-pure)/es|stable|actual|full/iterator/zip-keyed

Iterator.zip([
  [0, 1, 2],
  [3, 4, 5],
]).toArray();  // => [[0, 3], [1, 4], [2, 5]]

Iterator.zipKeyed({
  a: [0, 1, 2],
  b: [3, 4, 5, 6],
  c: [7, 8, 9],
}, {
  mode: 'longest',
  padding: { c: 10 },
}).toArray();
/*
[
  { a: 0,         b: 3, c: 7  },
  { a: 1,         b: 4, c: 8  },
  { a: 2,         b: 5, c: 9  },
  { a: undefined, b: 6, c: 10 },
];
 */

class Object {
  static entries(object: Object): Array<[string, mixed]>;
  static values(object: any): Array<mixed>;
}

core-js/proposals/object-values-entries

class Object {
  static fromEntries(iterable: Iterable<[key, value]>): Object;
}

core-js/proposals/object-from-entries

class Object {
  static getOwnPropertyDescriptors(object: any): { [property: PropertyKey]: PropertyDescriptor };
}

core-js/proposals/object-getownpropertydescriptors

class Object {
  static hasOwn(object: object, key: PropertyKey): boolean;
}

core-js/proposals/accessible-object-hasownproperty

class String {
  padStart(length: number, fillStr?: string = ' '): string;
  padEnd(length: number, fillStr?: string = ' '): string;
}

core-js/proposals/string-padding

class String {
  matchAll(regexp: RegExp): Iterator;
}

core-js/proposals/string-match-all

class String {
  replaceAll(searchValue: string | RegExp, replaceString: string | (searchValue, index, this) => string): string;
}

core-js/proposals/string-replace-all-stage-4

class String {
  trimLeft(): string;
  trimRight(): string;
  trimStart(): string;
  trimEnd(): string;
}

core-js/proposals/string-left-right-trim

// patched for support `RegExp` dotAll (`s`) flag:
class RegExp {
  constructor(pattern: RegExp | string, flags?: string): RegExp;
  exec(): Array<string | undefined> | null;
  readonly attribute dotAll: boolean;
  readonly attribute flags: string;
}

core-js/proposals/regexp-dotall-flag

// patched for support `RegExp` named capture groups:
class RegExp {
  constructor(pattern: RegExp | string, flags?: string): RegExp;
  exec(): Array<string | undefined> | null;
  @@replace(string: string, replaceValue: Function | string): string;
}

core-js/proposals/regexp-named-groups

class RegExp {
  static escape(value: string): string
}

core-js/proposals/regexp-escaping

class Promise {
  static allSettled(iterable: Iterable): Promise;
}

core-js/proposals/promise-all-settled

class AggregateError {
  constructor(errors: Iterable, message: string): AggregateError;
  errors: Array<any>;
  message: string;
}

class Promise {
  static any(promises: Iterable): Promise<any>;
}

core-js/proposals/promise-any

class Promise {
  finally(onFinally: Function): Promise;
}

core-js/proposals/promise-finally

class Promise {
  static try(callbackfn: Function, ...args?: Array<mixed>): Promise;
}

core-js/proposals/promise-try

class Promise {
  static withResolvers(): { promise: Promise, resolve: function, reject: function };
}

core-js/proposals/promise-with-resolvers

class Symbol {
  static asyncIterator: @@asyncIterator;
}

core-js/proposals/async-iteration

class Symbol {
  readonly attribute description: string | void;
}

core-js/proposals/symbol-description

namespace JSON {
  isRawJSON(O: any): boolean;
  // patched for source support
  parse(text: string, reviver?: (this: any, key: string, value: any, context: { source?: string }) => any): any;
  rawJSON(text: any): RawJSON;
  // patched for `JSON.rawJSON` support
  stringify(value: any, replacer?: Array<string | number> | (this: any, key: string, value: any) => any, space?: string | number): string | void;
}

core-js/proposals/json-parse-with-source

namespace JSON {
  stringify(target: any, replacer?: Function | Array, space?: string | number): string | void;
}

core-js/proposals/well-formed-stringify

class String {
  isWellFormed(): boolean;
  toWellFormed(): string;
}

core-js/proposals/well-formed-unicode-strings

class Set {
  difference(other: SetLike<mixed>): Set;
  intersection(other: SetLike<mixed>): Set;
  isDisjointFrom(other: SetLike<mixed>): boolean;
  isSubsetOf(other: SetLike<mixed>): boolean;
  isSupersetOf(other: SetLike<mixed>): boolean;
  symmetricDifference(other: SetLike<mixed>): Set;
  union(other: SetLike<mixed>): Set;
}

core-js/proposals/set-methods-v2

class Map {
  getOrInsert(key: any, value: any): any;
  getOrInsertComputed(key: any, (key: any) => value: any): any;
}

class WeakMap {
  getOrInsert(key: object | symbol, value: any): any;
  getOrInsertComputed(key: object | symbol, (key: any) => value: any): any;
}

core-js/proposals/map-upsert-v4

namespace Math {
  sumPrecise(items: Iterable<number>): Number;
}

core-js/proposals/math-sum

core-js(-pure)/stage/3

class Iterator {
  chunks(chunkSize: number): Iterator<any>;
  windows(windowSize: number, undersized?: 'only-full' | 'allow-partial' | undefined): Iterator<any>;
}

core-js/proposals/iterator-chunking-v2
core-js(-pure)/actual|full/iterator/chunks
core-js(-pure)/actual|full/iterator/windows

const digits = () => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].values();

let chunks = Array.from(digits().chunks(2));  // [[0, 1], [2, 3], [4, 5], [6, 7], [8, 9]]

let windows = Array.from(digits().windows(2));  // [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7], [7, 8], [8, 9]]

let windowsPartial = Array.from([0, 1].values().windows(3, 'allow-partial'));  // [[0, 1]]

let windowsFull = Array.from([0, 1].values().windows(3));  // []

class Iterator {
  includes(searchElement: any, skippedElements?: number): boolean;
}

core-js/proposals/iterator-includes
core-js(-pure)/actual|full/iterator/includes

[1, 2, 3].values().includes(2);     // => true
[1, 2, 3].values().includes(4);     // => false
[NaN].values().includes(NaN);       // => true
[1, 2, 3].values().includes(3, 2);  // => true
[1, 2, 3].values().includes(1, 1);  // => false

class Iterator {
  join(separator?: string): string;
}

core-js/proposals/iterator-join
core-js(-pure)/actual|full/iterator/join

[1, 2, 3].values().join();     // => '1,2,3'
[1, 2, 3].values().join('-');  // => '1-2-3'
[1, null, 3].values().join();  // => '1,,3'

class Promise {
  allKeyed(obj: Record<string | symbol, any>): Promise<Record<string | symbol, any>>;
  allSettledKeyed(obj: Record<string | symbol, any>): Promise<Record<string | symbol, { status: 'fulfilled', value: any } | { status: 'rejected', reason: any }>>;
}

core-js/proposals/await-dictionary
core-js(-pure)/actual|full/promise/all-keyed
core-js(-pure)/actual|full/promise/all-settled-keyed

await Promise.allKeyed({
  a: Promise.resolve(1),
  b: Promise.resolve(2),
  c: 3,
}); // => { a: 1, b: 2, c: 3 }

await Promise.allSettledKeyed({
  a: Promise.resolve(1),
  b: Promise.reject(2),
  c: 3,
}); // => { a: { status: "fulfilled", value: 1 }, b: { status: "rejected", reason: 2 }, c: { status: "fulfilled", value: 3 } }

core-js(-pure)/stage/2.7

class Symbol {
  static metadata: @@metadata;
}

class Function {
  @@metadata: null;
}

core-js/proposals/decorator-metadata-v2
core-js(-pure)/actual|full/symbol/metadata
core-js(-pure)/actual|full/function/metadata

core-js(-pure)/stage/2

class Iterator {
  toAsync(): AsyncIterator<any>;
}

class AsyncIterator {
  static from(iterable: AsyncIterable<any> | Iterable<any> | AsyncIterator<any>): AsyncIterator<any>;
  drop(limit: uint): AsyncIterator<any>;
  every(async callbackfn: (value: any, counter: uint) => boolean): Promise;
  filter(async callbackfn: (value: any, counter: uint) => boolean): AsyncIterator<any>;
  find(async callbackfn: (value: any, counter: uint) => boolean)): Promise<any>;
  flatMap(async callbackfn: (value: any, counter: uint) => AsyncIterable<any> | Iterable<any> | AsyncIterator<any>): AsyncIterator<any>;
  forEach(async callbackfn: (value: any, counter: uint) => void): Promise<void>;
  map(async callbackfn: (value: any, counter: uint) => any): AsyncIterator<any>;
  reduce(async callbackfn: (memo: any, value: any, counter: uint) => any, initialValue: any): Promise<any>;
  some(async callbackfn: (value: any, counter: uint) => boolean): Promise;
  take(limit: uint): AsyncIterator<any>;
  toArray(): Promise<Array>;
  @@toStringTag: 'AsyncIterator'
}

core-js/proposals/async-iterator-helpers
core-js(-pure)/actual|full/async-iterator
core-js(-pure)/actual|full/async-iterator/drop
core-js(-pure)/actual|full/async-iterator/every
core-js(-pure)/actual|full/async-iterator/filter
core-js(-pure)/actual|full/async-iterator/find
core-js(-pure)/actual|full/async-iterator/flat-map
core-js(-pure)/actual|full/async-iterator/for-each
core-js(-pure)/actual|full/async-iterator/from
core-js(-pure)/actual|full/async-iterator/map
core-js(-pure)/actual|full/async-iterator/reduce
core-js(-pure)/actual|full/async-iterator/some
core-js(-pure)/actual|full/async-iterator/take
core-js(-pure)/actual|full/async-iterator/to-array
core-js(-pure)/actual|full/iterator/to-async

await AsyncIterator.from([1, 2, 3, 4, 5, 6, 7])
  .drop(1)
  .take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

await [1, 2, 3].values().toAsync().map(async it => it ** 2).toArray(); // => [1, 4, 9]

const configurator = require('core-js/configurator');

configurator({ USE_FUNCTION_CONSTRUCTOR: true });

require('core-js/actual/async-iterator');

(async function * () { /* empty */ })() instanceof AsyncIterator; // => true

const configurator = require('core-js/configurator');

const { getPrototypeOf } = Object;

configurator({ AsyncIteratorPrototype: getPrototypeOf(getPrototypeOf(getPrototypeOf(async function * () { /* empty */ }()))) });

require('core-js/actual/async-iterator');

(async function * () { /* empty */ })() instanceof AsyncIterator; // => true

class Iterator {
  range(start: number, end: number, options: { step: number = 1, inclusive: boolean = false } | step: number = 1): NumericRangeIterator;
  range(start: bigint, end: bigint | Infinity | -Infinity, options: { step: bigint = 1n, inclusive: boolean = false } | step: bigint = 1n): NumericRangeIterator;
}

core-js/proposals/number-range
core-js(-pure)/full/iterator/range

for (const i of Iterator.range(1, 10)) {
  console.log(i); // => 1, 2, 3, 4, 5, 6, 7, 8, 9
}

for (const i of Iterator.range(1, 10, { step: 3, inclusive: true })) {
  console.log(i); // => 1, 4, 7, 10
}

class Array {
  static isTemplateObject(value: any): boolean
}

core-js/proposals/array-is-template-object
core-js(-pure)/full/array/is-template-object

console.log(Array.isTemplateObject((it => it)`qwe${ 123 }asd`)); // => true

class Number {
  clamp(min: number, max: number): number;
}

core-js/proposals/math-clamp-v2
core-js(-pure)/full/number/clamp

5.0.clamp(0, 10); // => 5
-5.0.clamp(0, 10); // => 0
15.0.clamp(0, 10); // => 10

class String {
  static dedent(templateOrTag: { raw: Array<string> } | function, ...substitutions: Array<string>): string | function;
}

core-js/proposals/string-dedent
core-js(-pure)/full/string/dedent

const message = 42;

console.log(String.dedent`
  print('${ message }')
`); // => print('42')

String.dedent(console.log)`
  print('${ message }')
`; // => ["print('", "')", raw: Array(2)], 42

class Symbol {
  static isRegisteredSymbol(value: any): boolean;
  static isWellKnownSymbol(value: any): boolean;
}

core-js/proposals/symbol-predicates-v2
core-js(-pure)/full/symbol/is-registered-symbol
core-js(-pure)/full/symbol/is-well-known-symbol

Symbol.isRegisteredSymbol(Symbol.for('key')); // => true
Symbol.isRegisteredSymbol(Symbol('key')); // => false

Symbol.isWellKnownSymbol(Symbol.iterator); // => true
Symbol.isWellKnownSymbol(Symbol('key')); // => false

class Symbol {
  static customMatcher: @@customMatcher;
}

core-js/proposals/pattern-extractors
core-js(-pure)/full/symbol/custom-matcher

core-js(-pure)/stage/1

class Observable {
  constructor(subscriber: Function): Observable;
  subscribe(observer: Function | { next?: Function, error?: Function, complete?: Function }): Subscription;
  @@observable(): this;
  static of(...items: Array<mixed>): Observable;
  static from(x: Observable | Iterable): Observable;
  static readonly attribute @@species: this;
}

class Symbol {
  static observable: @@observable;
}

core-js/proposals/observable
core-js(-pure)/full/observable
core-js(-pure)/full/symbol/observable

new Observable(observer => {
  observer.next('hello');
  observer.next('world');
  observer.complete();
}).subscribe({
  next(it) { console.log(it); },
  complete() { console.log('!'); },
});

/* Detailed source-code truncated for AI context efficiency. */

core-js/proposals/collection-methods
core-js/proposals/collection-of-from
core-js(-pure)/full/set/add-all
core-js(-pure)/full/set/delete-all
core-js(-pure)/full/set/every
core-js(-pure)/full/set/filter
core-js(-pure)/full/set/find
core-js(-pure)/full/set/from
core-js(-pure)/full/set/join
core-js(-pure)/full/set/map
core-js(-pure)/full/set/of
core-js(-pure)/full/set/reduce
core-js(-pure)/full/set/some
core-js(-pure)/full/map/delete-all
core-js(-pure)/full/map/every
core-js(-pure)/full/map/filter
core-js(-pure)/full/map/find
core-js(-pure)/full/map/find-key
core-js(-pure)/full/map/from
core-js(-pure)/full/map/includes
core-js(-pure)/full/map/key-by
core-js(-pure)/full/map/key-of
core-js(-pure)/full/map/map-keys
core-js(-pure)/full/map/map-values
core-js(-pure)/full/map/merge
core-js(-pure)/full/map/of
core-js(-pure)/full/map/reduce
core-js(-pure)/full/map/some
core-js(-pure)/full/map/update
core-js(-pure)/full/weak-set/add-all
core-js(-pure)/full/weak-set/delete-all
core-js(-pure)/full/weak-set/of
core-js(-pure)/full/weak-set/from
core-js(-pure)/full/weak-map/delete-all
core-js(-pure)/full/weak-map/of
core-js(-pure)/full/weak-map/from

Set.of(1, 2, 3, 2, 1); // => Set {1, 2, 3}

Map.from([[1, 2], [3, 4]], ([key, value]) => [key ** 2, value ** 2]); // => Map { 1: 4, 9: 16 }

function compositeKey(...args: Array<mixed>): object;
function compositeSymbol(...args: Array<mixed>): symbol;

core-js/proposals/keys-composition
core-js(-pure)/full/composite-key
core-js(-pure)/full/composite-symbol

// returns a symbol
const symbol = compositeSymbol({});
console.log(typeof symbol); // => 'symbol'

// works the same, but returns a plain frozen object without a prototype
const key = compositeKey({});
console.log(typeof key); // => 'object'
console.log({}.toString.call(key)); // => '[object Object]'
console.log(Object.getPrototypeOf(key)); // => null
console.log(Object.isFrozen(key)); // => true

const a = ['a'];
const b = ['b'];
const c = ['c'];

/* eslint-disable no-self-compare -- example */
console.log(compositeSymbol(a) === compositeSymbol(a)); // => true
console.log(compositeSymbol(a) !== compositeSymbol(['a'])); // => true
console.log(compositeSymbol(a, 1) === compositeSymbol(a, 1)); // => true
console.log(compositeSymbol(a, b) !== compositeSymbol(b, a)); // => true
console.log(compositeSymbol(a, b, c) === compositeSymbol(a, b, c)); // => true
console.log(compositeSymbol(1, a) === compositeSymbol(1, a)); // => true
console.log(compositeSymbol(1, a, 2, b) === compositeSymbol(1, a, 2, b)); // => true
console.log(compositeSymbol(a, a) === compositeSymbol(a, a)); // => true

class Array {
  filterReject(callbackfn: (value: any, index: number, target: any) => boolean, thisArg?: any): Array<mixed>;
}

class %TypedArray% {
  filterReject(callbackfn: (value: number, index: number, target: %TypedArray%) => boolean, thisArg?: any): %TypedArray%;
}

core-js/proposals/array-filtering-stage-1
core-js(-pure)/full/array(/virtual)/filter-reject
core-js/full/typed-array/filter-reject

[1, 2, 3, 4, 5].filterReject(it => it % 2); // => [2, 4]

class Array {
  uniqueBy(resolver?: (item: any) => any): Array<mixed>;
}

class %TypedArray% {
  uniqueBy(resolver?: (item: any) => any): %TypedArray%;;
}

core-js/proposals/array-unique
core-js(-pure)/full/array(/virtual)/unique-by
core-js/full/typed-array/unique-by

[1, 2, 3, 2, 1].uniqueBy(); // [1, 2, 3]

[
  { id: 1, uid: 10000 },
  { id: 2, uid: 10000 },
  { id: 3, uid: 10001 },
].uniqueBy(it => it.uid);    // => [{ id: 1, uid: 10000 }, { id: 3, uid: 10001 }]

class DataView {
  getUint8Clamped(offset: any): uint8
  setUint8Clamped(offset: any, value: any): void;
}

core-js/proposals/data-view-get-set-uint8-clamped
core-js/full/dataview/get-uint8-clamped
core-js/full/dataview/set-uint8-clamped

const view = new DataView(new ArrayBuffer(1));
view.setUint8Clamped(0, 100500);
console.log(view.getUint8Clamped(0)); // => 255

class Number {
  fromString(string: string, radix: number): number;
}

core-js/proposals/number-from-string
core-js(-pure)/full/number/from-string

class String {
  static cooked(template: Array<string>, ...substitutions: Array<string>): string;
}

core-js/proposals/string-cooked
core-js(-pure)/full/string/cooked

function safePath(strings, ...subs) {
  return String.cooked(strings, ...subs.map(sub => encodeURIComponent(sub)));
}

let id = 'spottie?';

safePath`/cats/${ id }`; // => /cats/spottie%3F

class String {
  codePoints(): Iterator<{ codePoint, position }>;
}

core-js/proposals/string-code-points
core-js(-pure)/full/string/code-points

for (let { codePoint, position } of 'qwe'.codePoints()) {
  console.log(codePoint); // => 113, 119, 101
  console.log(position);  // => 0, 1, 2
}

class Symbol {
  static customMatcher: @@customMatcher;
}

core-js/proposals/pattern-matching-v2
core-js(-pure)/full/symbol/custom-matcher

core-js(-pure)/stage/0

class Function {
  demethodize(): Function;
}

core-js/proposals/function-demethodize
core-js(-pure)/full/function/demethodize
core-js(-pure)/full/function/virtual/demethodize

const slice = Array.prototype.slice.demethodize();

slice([1, 2, 3], 1); // => [2, 3]

class Function {
  static isCallable(value: any): boolean;
  static isConstructor(value: any): boolean;
}

core-js/proposals/function-is-callable-is-constructor
core-js(-pure)/full/function/is-callable
core-js(-pure)/full/function/is-constructor

/* eslint-disable prefer-arrow-callback -- example */
Function.isCallable(null);                        // => false
Function.isCallable({});                          // => false
Function.isCallable(function () { /* empty */ }); // => true
Function.isCallable(() => { /* empty */ });       // => true
Function.isCallable(class { /* empty */ });       // => false

Function.isConstructor(null);                        // => false
Function.isConstructor({});                          // => false
Function.isConstructor(function () { /* empty */ }); // => true
Function.isConstructor(() => { /* empty */ });       // => false
Function.isConstructor(class { /* empty */ });       // => true

core-js(-pure)/stage/pre

namespace Reflect {
  defineMetadata(metadataKey: any, metadataValue: any, target: Object, propertyKey?: PropertyKey): void;
  getMetadata(metadataKey: any, target: Object, propertyKey?: PropertyKey): any;
  getOwnMetadata(metadataKey: any, target: Object, propertyKey?: PropertyKey): any;
  hasMetadata(metadataKey: any, target: Object, propertyKey?: PropertyKey): boolean;
  hasOwnMetadata(metadataKey: any, target: Object, propertyKey?: PropertyKey): boolean;
  deleteMetadata(metadataKey: any, target: Object, propertyKey?: PropertyKey): boolean;
  getMetadataKeys(target: Object, propertyKey?: PropertyKey): Array<mixed>;
  getOwnMetadataKeys(target: Object, propertyKey?: PropertyKey): Array<mixed>;
  metadata(metadataKey: any, metadataValue: any): decorator(target: Object, targetKey?: PropertyKey) => void;
}

core-js/proposals/reflect-metadata
core-js(-pure)/full/reflect/define-metadata
core-js(-pure)/full/reflect/delete-metadata
core-js(-pure)/full/reflect/get-metadata
core-js(-pure)/full/reflect/get-metadata-keys
core-js(-pure)/full/reflect/get-own-metadata
core-js(-pure)/full/reflect/get-own-metadata-keys
core-js(-pure)/full/reflect/has-metadata
core-js(-pure)/full/reflect/has-own-metadata
core-js(-pure)/full/reflect/metadata

let object = {};
Reflect.defineMetadata('foo', 'bar', object);
Reflect.ownKeys(object);               // => []
Reflect.getOwnMetadataKeys(object);    // => ['foo']
Reflect.getOwnMetadata('foo', object); // => 'bar'

getter self: GlobalThisValue;

core-js(-pure)/stable|actual|full/self

// eslint-disable-next-line no-restricted-globals -- example
self.Array === Array; // => true

function structuredClone(value: Serializable, { transfer?: Sequence }): any;

core-js(-pure)/stable|actual|full/structured-clone

const structured = [{ a: 42 }];
const sclone = structuredClone(structured);
console.log(sclone);                      // => [{ a: 42 }]
console.log(structured !== sclone);       // => true
console.log(structured[0] !== sclone[0]); // => true

const circular = {};
circular.circular = circular;
const cclone = structuredClone(circular);
console.log(cclone.circular === cclone);  // => true

structuredClone(42);                                            // => 42
structuredClone({ x: 42 });                                     // => { x: 42 }
structuredClone([1, 2, 3]);                                     // => [1, 2, 3]
structuredClone(new Set([1, 2, 3]));                            // => Set{ 1, 2, 3 }
structuredClone(new Map([['a', 1], ['b', 2]]));                 // => Map{ a: 1, b: 2 }
structuredClone(new Int8Array([1, 2, 3]));                      // => new Int8Array([1, 2, 3])
structuredClone(new AggregateError([1, 2, 3], 'message'));      // => new AggregateError([1, 2, 3], 'message'))
structuredClone(new TypeError('message', { cause: 42 }));       // => new TypeError('message', { cause: 42 })
structuredClone(new DOMException('message', 'DataCloneError')); // => new DOMException('message', 'DataCloneError')
structuredClone(document.getElementById('myfileinput'));        // => new FileList
structuredClone(new DOMPoint(1, 2, 3, 4));                      // => new DOMPoint(1, 2, 3, 4)
structuredClone(new Blob(['test']));                            // => new Blob(['test'])
structuredClone(new ImageData(8, 8));                           // => new ImageData(8, 8)
// etc.

structuredClone(new WeakMap()); // => DataCloneError on non-serializable types

function atob(data: string): string;
function btoa(data: string): string;

core-js(-pure)/stable|actual|full/atob
core-js(-pure)/stable|actual|full/btoa

btoa('hi, core-js');      // => 'aGksIGNvcmUtanM='
atob('aGksIGNvcmUtanM='); // => 'hi, core-js'

function setTimeout(callback: any, time: any, ...args: Array<mixed>): number;
function setInterval(callback: any, time: any, ...args: Array<mixed>): number;

core-js(-pure)/stable|actual|full/set-timeout
core-js(-pure)/stable|actual|full/set-interval

// Before:
setTimeout(log.bind(null, 42), 1000);
// After:
setTimeout(log, 1000, 42);

function setImmediate(callback: any, ...args: Array<mixed>): number;
function clearImmediate(id: number): void;

core-js(-pure)/stable|actual|full/set-immediate
core-js(-pure)/stable|actual|full/clear-immediate

setImmediate((arg1, arg2) => {
  console.log(arg1, arg2); // => Message will be displayed with minimum delay
}, 'Message will be displayed', 'with minimum delay');

clearImmediate(setImmediate(() => {
  console.log('Message will not be displayed');
}));

function queueMicrotask(fn: Function): void;

core-js(-pure)/stable|actual|full/queue-microtask

queueMicrotask(() => console.log('called as microtask'));

class URL {
  constructor(url: string, base?: string);
  attribute href: string;
  readonly attribute origin: string;
  attribute protocol: string;
  attribute username: string;
  attribute password: string;
  attribute host: string;
  attribute hostname: string;
  attribute port: string;
  attribute pathname: string;
  attribute search: string;
  readonly attribute searchParams: URLSearchParams;
  attribute hash: string;
  toJSON(): string;
  toString(): string;
  static canParse(url: string, base?: string): boolean;
  static parse(url: string, base?: string): URL | null;
}

class URLSearchParams {
  constructor(params?: string | Iterable<[key, value]> | Object);
  append(name: string, value: string): void;
  delete(name: string, value?: string): void;
  get(name: string): string | void;
  getAll(name: string): Array<string>;
  has(name: string, value?: string): boolean;
  set(name: string, value: string): void;
  sort(): void;
  toString(): string;
  forEach(callbackfn: (value: any, index: number, target: any) => void, thisArg: any): void;
  entries(): Iterator<[key, value]>;
  keys(): Iterator<key>;
  values(): Iterator<value>;
  @@iterator(): Iterator<[key, value]>;
  readonly attribute size: number;
}

core-js/proposals/url
core-js(-pure)/stable|actual|full/url
core-js(-pure)/stable|actual|full/url/can-parse
core-js/stable|actual|full/url/to-json
core-js(-pure)/stable|actual|full/url-search-params

/* Detailed source-code truncated for AI context efficiency. */

class DOMException {
  constructor(message: string, name?: string);
  readonly attribute name: string;
  readonly attribute message: string;
  readonly attribute code: string;
  attribute stack: string; // in engines that should have it
  @@toStringTag: 'DOMException';
}

core-js(-pure)/stable|actual|full/dom-exception
core-js(-pure)/stable|actual|full/dom-exception/constructor
core-js/stable|actual|full/dom-exception/to-string-tag

const exception = new DOMException('error', 'DataCloneError');
console.log(exception.name);                            // => 'DataCloneError'
console.log(exception.message);                         // => 'error'
console.log(exception.code);                            // => 25
console.log(typeof exception.stack);                    // => 'string'
console.log(exception instanceof DOMException);         // => true
console.log(exception instanceof Error);                // => true
console.log(exception.toString());                      // => 'DataCloneError: error'
console.log(Object.prototype.toString.call(exception)); // => '[object DOMException]'

class [
  CSSRuleList,
  CSSStyleDeclaration,
  CSSValueList,
  ClientRectList,
  DOMRectList,
  DOMStringList,
  DataTransferItemList,
  FileList,
  HTMLAllCollection,
  HTMLCollection,
  HTMLFormElement,
  HTMLSelectElement,
  MediaList,
  MimeTypeArray,
  NamedNodeMap,
  PaintRequestList,
  Plugin,
  PluginArray,
  SVGLengthList,
  SVGNumberList,
  SVGPathSegList,
  SVGPointList,
  SVGStringList,
  SVGTransformList,
  SourceBufferList,
  StyleSheetList,
  TextTrackCueList,
  TextTrackList,
  TouchList,
] {
  @@iterator(): Iterator<value>;
}

class [DOMTokenList, NodeList] {
  forEach(callbackfn: (value: any, index: number, target: any) => void, thisArg: any): void;
  entries(): Iterator<[key, value]>;
  keys(): Iterator<key>;
  values(): Iterator<value>;
  @@iterator(): Iterator<value>;
}

core-js(-pure)/stable|actual|full/dom-collections/iterator
core-js/stable|actual|full/dom-collections/for-each

for (let { id } of document.querySelectorAll('*')) {
  if (id) console.log(id);
}

for (let [index, { id }] of document.querySelectorAll('*').entries()) {
  if (id) console.log(index, id);
}

document.querySelectorAll('*').forEach(it => console.log(it.id));

function isIterable(value: any): boolean;
function getIterator(value: any): Object;
function getIteratorMethod(value: any): Function | void;

core-js-pure/es|stable|actual|full/is-iterable
core-js-pure/es|stable|actual|full/get-iterator
core-js-pure/es|stable|actual|full/get-iterator-method

import isIterable from 'core-js-pure/actual/is-iterable';
import getIterator from 'core-js-pure/actual/get-iterator';
import getIteratorMethod from 'core-js-pure/actual/get-iterator-method';

let list = (function () {
  // eslint-disable-next-line prefer-rest-params -- example
  return arguments;
})(1, 2, 3);

console.log(isIterable(list)); // true;

let iterator = getIterator(list);
console.log(iterator.next().value); // 1
console.log(iterator.next().value); // 2
console.log(iterator.next().value); // 3
console.log(iterator.next().value); // undefined

getIterator({}); // TypeError: [object Object] is not iterable!

let method = getIteratorMethod(list);
console.log(typeof method);         // 'function'
iterator = method.call(list);
console.log(iterator.next().value); // 1
console.log(iterator.next().value); // 2
console.log(iterator.next().value); // 3
console.log(iterator.next().value); // undefined

console.log(getIteratorMethod({})); // undefined

import 'https://deno.land/x/[email protected]/index.js'; // <- at the top of your entry point

Object.hasOwn({ foo: 42 }, 'foo');   // => true

[1, 2, 3, 4, 5, 6, 7].at(-3);        // => 5

[1, 2, 3, 4, 5].group(it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }

Promise.any([
  Promise.resolve(1),
  Promise.reject(2),
  Promise.resolve(3),
]).then(console.log);                // => 1

(function * (i) { while (true) yield i++; })(1)
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray();                        // => [9, 25]

// 使用 `core-js` 全部功能打补丁：
import "core-js";
// 仅仅使用稳定的 `core-js` 功能 - ES 和 web 标准：
import "core-js/stable";
// 仅仅使用稳定的 ES 功能
import "core-js/es";

// 如果你想用 `Set` 的补丁
// 所有 `Set`- ES 提案中，相关的功能：
import "core-js/features/set";
// 稳定的 `Set` ES 功能和来自web标准的功能
// （DOM 集合迭代器）
import "core-js/stable/set";
// 只有 `Set` 所需的稳定的 ES 功能
import "core-js/es/set";
// 与上面一致，但不会污染全局命名空间
import Set from "core-js-pure/features/set";
import Set from "core-js-pure/stable/set";
import Set from "core-js-pure/es/set";


// 仅仅为需要的方法打补丁
import "core-js/feature/set/intersection";
import "core-js/stable/queque-microtask";
import "core-js/es/array/from";

// 为 reflect metadata 提案打补丁
import "core-js/proposals/reflect-metadata";
// 为所有 stage 2+ 的提案打补丁
import "core-js/stage/2";

import "@babel/polyfill";

import "core-js/stable";
import "regenerator-runtime/runtime";

npm i --save core-js regenerator-runtime

import "core-js/stable";
import "regenerator-runtime/runtime";

import "core-js/modules/es.array.unscopables.flat";
import "core-js/modules/es.array.unscopaables.flat-map";
import "core-js/modules/es.object.from-entries";
import "core-js/modules/web.immediate";

import "core-js/modules/web.immediate";

import "core-js/es";
import "core-js/proposals/set-methods";
import "core-js/features/set/map";

import "core-js/modules/es.array.unscopables.flat";
import "core-js/modules/es.array.unscopables.flat-map";
import "core-js/modules/es.object.from-entries";
import "core-js/modules/esnext.set.difference";
import "core-js/modules/esnext.set.intersection";
import "core-js/modules/esnext.set.is-disjoint-from";
import "core-js/modules/esnext.set.is-subset-of";
import "core-js/modules/esnext.set.is-superset-of";
import "core-js/modules/esnext.set.map";
import "core-js/modules/esnext.set.symmetric-difference";
import "core-js/modules/esnext.set.union";

const set = new Set([1, 2, 3]);
[1, 2, 3].includes(2);

import "core-js/modules/es.array.includes";
import "core-js/modules/es.array.iterator";
import "core-js/modules/es.object.to-string";
import "core-js/modules/es.set";

const set = new Set([1, 2, 3]);
[1, 2, 3].includes(2);

const set = new Set([1, 2, 3]);
[1, 2, 3].includes(2);

array.includes(something);

import _includesInstanceProperty from "@babel/runtime-corejs3/core-js-stable/instance/includes";

_includesInstanceProperty(array).call(array, something);

new Set([1, 2, 3, 2, 1]);
string.matchAll(/something/g);

import _Set from "@babel/runtime-corejs/core-js-stable/set";

new _Set([1, 2, 3, 2, 1]);
string.matchAll(/something/g);

import _Set from "@babel/runtime-corejs3/core-js/set";
import _matchAllInstanceProperty from "@babel/runtime-corejs/core-js/instance/match-all";

new _Set([1, 2, 3, 2, 1]);
_matchAllInstanceProperty(string).call(string, /something/g);

myArrayLikeObject[Symbol.iterator] = Array.prototype[Symbol.iterator];

StandardLibraryRegistry.get(moduleName);
StandardLibraryRegistry.set(moduleName, value);