; } ``` This is an example of using it with ES2015 classes: ```jsx import { linkEvent, Component } from 'inferno'; function handleClick(instance, event) { instance.setState({ data: event.target.value }); } class MyComponent extends Component { render () { return

; } } ``` `linkEvent()` offers better performance than binding an event in a class constructor and using arrow functions, so use it where possible. ## Controlled Components In HTML, form elements such as ``, `

`, and `<select>` typically maintain their own state and update it based on user input.
In Inferno, mutable state is typically kept in the state property of components, and only updated with `setState()`.

We can combine the two by making the Inferno state be the "single source of truth". Then the Inferno component that renders a form also
controls what happens in that form on subsequent user input. An input form element whose value is controlled by
Inferno in this way is called a "controlled component".

## Inferno Top-Level API

### `render` (package: `inferno`)

```javascript
import { render } from 'inferno';

render(<div />, document.getElementById("app"));
```

Render a virtual node into the DOM in the supplied container given the supplied virtual DOM. If the virtual node was previously rendered
into the container, this will perform an update on it and only mutate the DOM as necessary, to reflect the latest Inferno virtual node.

Warning: If the container element is not empty before rendering, the content of the container will be overwritten on the initial render.

### `createRenderer` (package: `inferno`)

`createRenderer` creates an alternative render function with a signature matching that of the first argument passed to a reduce/scan function. This allows for easier integration with reactive programming libraries, like [RxJS](https://github.com/ReactiveX/rxjs) and [Most](https://github.com/cujojs/most).

```javascript
import { createRenderer } from 'inferno';
import { scan, map } from 'most';

const renderer = createRenderer();

// NOTE: vNodes$ represents a stream of virtual DOM node updates
scan(renderer, document.getElementById("app"), vNodes$);
```

See [inferno-most-fp-demo](https://github.com/joshburgess/inferno-most-fp-demo) for an example of how to build an app architecture around this.

### `createElement` (package: `inferno-create-element`)

Creates an Inferno VNode using a similar API to that found with React's `createElement()`

```javascript
import { Component, render } from 'inferno';
import { createElement } from 'inferno-create-element';

class BasicComponent extends Component {
  render() {
    return createElement('div', {
        className: 'basic'
      },
      createElement('span', {
        className: this.props.name
      }, 'The title is ', this.props.title)
    )
  }
}

render(
  createElement(BasicComponent, { title: 'abc' }),
  document.getElementById("app")
);
```

### `Component` (package: `inferno`)

**Class component:**

```javascript
import { Component } from 'inferno';

class MyComponent extends Component {
  render() {
      return <div>My Component</div>
  }
}
```

This is the base class for Inferno Components when they're defined using ES6 classes.

**Functional component:**

```javascript
const MyComponent = ({ name, age }) => (
  <span>My name is: { name } and my age is: {age}</span>
);
```

Another way of using defaultHooks.
```javascript
export function Static() {
    return <div>1</div>;
}

Static.defaultHooks = {
    onComponentShouldUpdate() {
        return false;
    }
};
```

Default props
```jsx
export function MyFunctionalComponent({value}) {
    return <div>{value}</div>;
}

MyFunctionalComponent.defaultProps = {
    value: 10
};

```

Functional components are first-class functions where their first argument is the `props` passed through from their parent.

### `createVNode` (package: `inferno`)
```js
import { createVNode } from 'inferno';

createVNode(
  flags,
  type,
  [className],
  [...children],
  [childFlags],
  [props],
  [key],
  [ref]
)
```

createVNode is used to create html element's virtual node object. Typically `createElement()` (package: `inferno-create-element`), `h()` (package: `inferno-hyperscript`) or JSX are used to create
`VNode`s for Inferno, but under the hood they all use `createVNode()`. Below is an example of `createVNode` usage:

```javascript
import { VNodeFlags, ChildFlags } from 'inferno-vnode-flags';
import { createVNode, createTextVNode, render } from 'inferno';

const vNode = createVNode(VNodeFlags.HtmlElement, 'div', 'example', createTextVNode('Hello world!'), ChildFlags.HasVNodeChildren);

// <div class="example">Hello world!</div>

render(vNode, container);
```

`createVNode` arguments explained:

`flags`: (number) is a value from [`VNodeFlags`](https://github.com/infernojs/inferno/tree/master/packages/inferno-vnode-flags), this is a numerical value that tells Inferno what the VNode describes on the page.

`type`: (string) is tagName for element for example 'div'

`className`: (string) is the class attribute ( it is separated from props because it is the most commonly used property )

`children`: (vNode[]|vNode) is one or array of vNodes to be added as children for this vNode

`childFlags`: (number) is a value from [`ChildFlags`](https://github.com/infernojs/inferno/tree/master/packages/inferno-vnode-flags), this tells inferno shape of the children so normalization process can be skipped.

`props`: (Object) is object containing all other properties. fe: `{onClick: method, 'data-attribute': 'Hello Community!}`

`key`: (string|number) unique key within this vNodes siblings to identify it during keyed algorithm.

`ref`: (function) callback which is called when DOM node is added/removed from DOM.

### `createComponentVNode` (package: 'inferno')
```js
import { createComponentVNode } from 'inferno';

createComponentVNode(
  flags,
  type,
  [props],
  [key],
  [ref]
)
```

createComponentVNode is used for creating vNode for Class/Functional Component.

Example:
```javascript
import { VNodeFlags, ChildFlags } from 'inferno-vnode-flags';
import { createVNode, createTextVNode, createComponentVNode, render } from 'inferno';

function MyComponent(props, context) {
  return createVNode(VNodeFlags.HtmlElement, 'div', 'example', createTextVNode(props.greeting), ChildFlags.HasVNodeChildren);
}

const vNode = createComponentVNode(VNodeFlags.ComponentFunction, MyComponent, {
  greeting: 'Hello Community!'
}, null, {
  onComponentDidMount() {
    console.log("example of did mount hook!")
  }
})

// <div class="example">Hello Community!</div>

render(vNode, container);
```

`createComponentVNode` arguments explained:

`type`: (Function/Class) is the class or function prototype for Component

`props`: (Object) properties passed to Component, can be anything

`key`: (string|number) unique key within this vNodes siblings to identify it during keyed algorithm.

`ref`: (Function|Object) this property is object for Functional Components defining all its lifecycle methods. For class Components this is function callback for ref.

### `createTextVNode` (package: 'inferno')

createTextVNode is used for creating vNode for text nodes.

`createTextVNode` arguments explained:
text: (string) is a value for text node to be created.
key: (string|number) unique key within this vNodes siblings to identify it during keyed algorithm.

```js
import { createTextVNode } from 'inferno';

createTextVNode(
  text,
  key
)
```

### `cloneVNode` (package: `inferno-clone-vnode`)

This package has same API as React.cloneElement

```javascript
import { cloneVNode } from 'inferno-clone-vnode';

cloneVNode(
  vNode,
  [props],
  [...children]
)
```

Clone and return a new Inferno `VNode` using a `VNode` as the starting point. The resulting `VNode` will have the original `VNode`'s props with the new props merged in shallowly. New children will replace existing children. key and ref from the original `VNode` will be preserved.

`cloneVNode()` is almost equivalent to:
```jsx
<VNode.type {...VNode.props} {...props}>{children}</VNode.type>
```

An example of using `cloneVNode`:

```javascript
import { createVNode, render } from 'inferno';
import { cloneVNode } from 'inferno-clone-vnode';
import { VNodeFlags } from 'inferno-vnode-flags';

const vNode = createVNode(VNodeFlags.HtmlElement, 'div', 'example', 'Hello world!');
const newVNode = cloneVNode(vNode, { id: 'new' }); // we are adding an id prop to the VNode

render(newVNode, container);
```

If you're using JSX:

```jsx
import { render } from 'inferno';
import { cloneVNode } from 'inferno-clone-vnode';

const vNode = <div className="example">Hello world</div>;
const newVNode = cloneVNode(vNode, { id: 'new' }); // we are adding an id prop to the VNode

render(newVNode, container);
```

### `createPortal` (package: 'inferno')

HTML:
```html
<div id="root"></div>
<div id="outside"></div>
```

Javascript:
```jsx
const { render, Component, version, createPortal } from 'inferno';

function Outsider(props) {
	return <div>{`Hello ${props.name}!`}</div>;
}

const outsideDiv = document.getElementById('outside');
const rootDiv = document.getElementById('root');

function App() {
	return (
  	    <div>
    	    Main view
            ...
            {createPortal(<Outsider name="Inferno" />, outsideDiv)}
        </div>
    );
}

// render an instance of Clock into <body>:
render(<App />, rootDiv);
```

Results into:
```html
<div id="root">
    <div>Main view ...</div>
</div>
<div id="outside">
    <div>Hello Inferno!</div>
</div>
```
Cool, huh? Updates (props/context) will flow into "Outsider" component from the App component the same way as any other Component.
For inspiration on how to use it click [here](https://hackernoon.com/using-a-react-16-portal-to-do-something-cool-2a2d627b0202)!

### `createRef` (package: `inferno`)

createRef API provides shorter syntax than callback ref when timing of element is not needed.

```jsx
import { Component, render, createRef } from 'inferno';

class Foobar extends Component {
  constructor(props) {
    super(props);

// Store reference somewhere
    this.element = createRef(); // Returns object {current: null}
  }

render() {
    return (
      <div>
        <span id="span" ref={this.element}>
          Ok
        </span>
      </div>
    );
  }
}

render(<Foobar />, container);
```

### `createFragment` (package: `inferno`)

createFragment is the native way to createFragment vNode. `createFragment(children: any, childFlags: ChildFlags, key?: string | number | null)`

`createFragment` arguments explained:

`children`: (Array) Content of fragment vNode, typically array of VNodes

`key`: (string|number) unique key within this vNodes siblings to identify it during keyed algorithm.

Alternative ways to create fragment vNode are:

- Using JSX `<> ... </>`, `<Fragment> .... </Fragment>` or `<Inferno.Fragment> ... </Inferno.Fragment>`
- Using createElement API `createElement(Inferno.Fragment, {key: 'test'}, ...children)`
- Using hyperscript API `h(Inferno.Fragment, {key: 'test'}, children)`

In the below example both fragments are identical except they have different key
```jsx
import { Fragment, render, createFragment } from 'inferno';
import { ChildFlags } from 'inferno-vnode-flags';

function Foobar() {
    return (
      <div $HasKeyedChildren>
        {createFragment(
            [<div>Ok</div>, <span>1</span>],
            ChildFlags.HasNonKeyedChildren,
            'key1'
        )}
        <Fragment key="key2">
          <div>Ok</div>
          <span>1</span>
        </Fragment>
      </div>
    );
}

render(<Foobar />, container);
```

### `forwardRef` (package: `inferno`)

forwardRef is a new mechanism to "forward" ref inside a functional Component.
It can be useful if you have simple functional Components and you want to create reference to a specific element inside it.

```jsx
import { forwardRef, Component, render } from 'inferno';

const FancyButton = forwardRef((props, ref) => (
  <button ref={ref} className="FancyButton">
    {props.children}
  </button>
));

class Hello extends Component {
  render() {
    return (
      <FancyButton
        ref={btn => {
          if (btn) {
            // btn variable is the button rendered from FancyButton
          }
        }}
      >
        Click me!
      </FancyButton>
    );
  }
}

render(<Hello />, container);
```

### `hydrate` (package: `inferno-hydrate`)

```javascript
import { hydrate } from 'inferno-hydrate';

hydrate(<div />, document.getElementById("app"));
```

Same as `render()`, but is used to hydrate a container whose HTML contents were rendered by `inferno-server`. Inferno will attempt to attach event listeners to the existing markup.

### `findDOMNode` (package: `inferno-extras`)
This feature has been moved from inferno to inferno-compat in v6. No options are needed anymore.

Note: we recommend using a `ref` callback on a component to find its instance, rather than using `findDOMNode()`. `findDOMNode()` cannot be used on functional components.

If a component has been mounted into the DOM, this returns the corresponding native browser DOM element. This method is useful for reading values out of the DOM, such as form field values and performing DOM measurements.
In most cases, you can attach a ref to the DOM node and avoid using `findDOMNode()` at all. When render returns null or false, `findDOMNode()` returns null.
If Component has rendered fragment it returns the first element.

### Inferno Flags (package: inferno-vnode-flags)

**VNodeFlags:**
- `VNodeFlags.HtmlElement`
- `VNodeFlags.ComponentUnknown`
- `VNodeFlags.ComponentClass`
- `VNodeFlags.ComponentFunction`
- `VNodeFlags.Text`
- `VNodeFlags.SvgElement`
- `VNodeFlags.InputElement`
- `VNodeFlags.TextareaElement`
- `VNodeFlags.SelectElement`
- `VNodeFlags.Portal`
- `VNodeFlags.ReCreate` (JSX **$ReCreate**) always re-creates the vNode
- `VNodeFlags.ContentEditable`
- `VNodeFlags.Fragment`
- `VNodeFlags.InUse`
- `VnodeFlags.ForwardRef`
- `VNodeFlags.Normalized`

**VNodeFlags Masks:**
- `VNodeFlags.ForwardRefComponent` Functional component wrapped in forward ref
- `VNodeFlags.FormElement` - Is form element
- `VNodeFlags.Element` - Is vNode element
- `VNodeFlags.Component` - Is vNode Component
- `VNodeFlags.DOMRef` - Bit set when vNode holds DOM reference
- `VNodeFlags.InUseOrNormalized` - VNode is used somewhere else or came from normalization process
- `VNodeFlags.ClearInUseNormalized` - Opposite mask of InUse or Normalized

**ChildFlags**
- `ChildFlags.UnknownChildren` needs Normalization
- `ChildFlags.HasInvalidChildren` is invalid (null, undefined, false, true)
- `ChildFlags.HasVNodeChildren` (JSX **$HasVNodeChildren**) is single vNode (Element/Component)
- `ChildFlags.HasNonKeyedChildren` (JSX **$HasNonKeyedChildren**) is Array of vNodes non keyed (no nesting, no holes)
- `ChildFlags.HasKeyedChildren` (JSX **$HasKeyedChildren**) is Array of vNodes keyed (no nesting, no holes)
- `ChildFlags.HasTextChildren` (JSX **$HasTextChildren**) vNode contains only text

**ChildFlags Masks**
- `ChildFlags.MultipleChildren` Is Array

### `renderToString` (package: `inferno-server`)

```javascript
import { renderToString } from 'inferno-server';

const string = renderToString(<div />);
```

Render a virtual node into an HTML string, given the supplied virtual DOM.

## Functional component lifecycle events

| Name                        | Triggered when                                                  | Arguments to callback           |
| -----------                 | --------------                                                  | -----------------------         |
| `onComponentWillMount`      | a functional component is about to mount                        |                                 |
| `onComponentDidMount`       | a functional component has mounted successfully                 | `domNode`                       |
| `onComponentShouldUpdate`   | a functional component has been triggered to update             | `lastProps, nextProps`          |
| `onComponentWillUpdate`     | a functional component is about to perform an update            | `lastProps, nextProps`          |
| `onComponentDidUpdate`      | a functional component has performed an update                  | `lastProps, nextProps`          |
| `onComponentWillUnmount`    | a functional component is about to be unmounted                 | `domNode`                       |
| `onComponentDidAppear`      | a functional component has mounted and is ready for animations  | `domNode, props`                |
| `onComponentWillDisappear`  | a functional component is unmounted before DOM node is removed  | `domNode, props, callback`      |

onComponentWillDisappear has special type of argument "callback" which needs to be called when component is ready to be removed from the DOM. fe. after animations are finished.

## Class component lifecycle events

All these Component lifecycle methods ( including `render` and `setState - callback`) are called with Component instance context. You don't need to "bind" these methods.

| Name                              | Triggered when                                                                        | Arguments to callback           |
| -----------                       | --------------                                                                        | -----------------------         |
| `componentDidMount`               | component has been mounted successfully                                                |                                 |
| `componentWillMount`              | component is about to mount                                                           |                                 |
| `componentWillReceiveProps`       | before render when component updates                                                  | `nextProps, context`            |
| `shouldComponentUpdate`           | component has been triggered to update                                                | `nextProps, nextState`          |
| `componentWillUpdate`             | component is about to perform an update                                               | `nextProps, nextState, context` |
| `componentDidUpdate`              | component has performed an update                                                     | `lastProps, lastState, snapshot`|
| `componentWillUnmount`            | component is about to be unmounted                                                    |                                 |
| `getChildContext`                 | before render method, return value object is combined to sub tree context             |                                 |
| `getSnapshotBeforeUpdate`         | before component updates, return value is sent to componentDidUpdate as 3rd parameter | `lastProps, lastState`          |
| `static getDerivedStateFromProps` | before render method                                                                  | `nextProps, state`              |
| `componentDidAppear`              | component has mounted and is ready for animations                                     | `domNode`                       |
| `componentWillDisappear`          | component is unmounted before DOM node is removed                                     | `domNode, callback`             |

componentWillDisappear has special type of argument "callback" which needs to be called when component is ready to be removed from the DOM. fe. after animations are finished.

### Using functional lifecycle events

Functional lifecycle events must be explicitly assigned via props onto a functional component like shown below:

```javascript
import { render } from 'inferno';

function mounted(domNode) {
  // [domNode] will be available for DOM nodes and components (if the component has mounted to the DOM)
}

function FunctionalComponent({ props }) {
  return <div>Hello world</div>;
}

render(
  <FunctionalComponent onComponentDidMount={ mounted } />,
  document.getElementById("app")
);
```

Please note: class components (ES2015 classes) from `inferno` **do not** support the same lifecycle events (they have their own lifecycle events that work as methods on the class itself).

## Development vs Production modes

By default, Inferno will run in development mode. Development mode provides extra checks and better error messages at the cost of slower performance and larger code to parse.
When using Inferno in a production environment, it is highly recommended that you turn off development mode.

### Running Inferno on Node JS

Ensure the environment variable `process.env.NODE_ENV` is set to `production`.

## Application bundling

When building your application bundle, ensure `process.env.NODE_ENV` is replaced with string`"development"` or `"production"` based on the workflow.
It is recommended to use [ts-plugin-inferno](https://github.com/infernojs/ts-plugin-inferno) for typescript TSX compilation and [babel-plugin-infeno](https://github.com/infernojs/babel-plugin-inferno) for javascript JSX compilation.

When building for development, you may want to use `inferno.dev.mjs` for v9 or newer and `inferno.dev.esm.js` for older than v9. That bundle file contains ES6 exports for better tree-shaking support, improved error messages and added validation to help fixing possible issues during development.
The file is found from `package.json` - `dev:module` entry point and the files are physically located in `node_modules/inferno/dist/` folder.
Remember that it is not recommended to use that file in production due to slower performance. For production usage use `node_modules/inferno/dist/inferno.mjs` -file for v9 or newer and `node_modules/inferno/dist/inferno.esm.js` -file for older than v9.

Example of **Webpack** configuration:

```js
const path = require('path');
const infernoTsx = require('ts-plugin-inferno').default;

... webpack config ...

module: {
        rules: [
            {
                test: /\.js$/, // Add "jsx" if your application uses `jsx` file extensions
                exclude: /node_modules/,
                use: [{
                    loader: 'babel-loader',
                    options: {
                        plugins: [
                            // Compile javascript JSX syntax using inferno's own plugin
                            ['babel-plugin-inferno', {imports: true}]
                        ]
                    }
                }]
            },
            {
                test: /\.ts+(|x)$/, // Compile ts and tsx extensions
                exclude: /node_modules/,
                use: [{
                    loader: 'ts-loader',
                    options: {
                        getCustomTransformers: () => ({
                            // inferno custom TSX plugin
                            after: [infernoTsx()]
                        }),
                        compilerOptions: {
                            /* typescript compiler options */
                        }
                    }
                }]
            }
        ]
    },
    resolve: {
        extensions: ['.js', '.ts', '.tsx'],
        alias: {
            // This maps import "inferno" to es6 module entry based on workflow
            inferno: path.resolve(__dirname, 'node_modules/inferno/dist', isProduction ? 'index.dev.mjs' : 'index.mjs')
        }
    },
    plugins: [
        new webpack.DefinePlugin({
            'process.env': {
                'NODE_ENV':  JSON.stringify(isProduction ? 'production' : 'development')
            }
        })
    ]
```

Example of **Rollup** configuration:

```js
const path = require('path');
const alias = require('@rollup/plugin-alias');
const {babel} = require('@rollup/plugin-babel');
const replace = require('@rollup/plugin-replace');
const typescript = require('rollup-plugin-typescript2');
const transformInferno = require('ts-plugin-inferno').default;

... Rollup config ...
{
    input: /* entry file */,
    plugins: [
            alias({
                resolve: ['.js'],
                entries: [
                    // This maps import "inferno" to es6 module entry based on workflow
                    {find: 'inferno', replacement: path.resolve(__dirname, 'node_modules/inferno/dist', isProduction ? 'index.dev.mjs' : 'index.mjs')}
                ]
            }),
            typescript({
                include: ['*.ts+(|x)', '**/*.ts+(|x)'],
                transformers: [
                    () => ({
                        after: [transformInferno()]
                    })
                ],
                tsconfig: 'tsconfig.json',
                tsconfigOverride: {
                    /* typescript compiler options */
                }
            }),
            babel({
                babelrc: false,
                sourceMaps: isDeploy,
                plugins: [
                    // Compile javascript JSX syntax using inferno's own plugin
                    ['babel-plugin-inferno', {imports: true}]
                ],
                babelHelpers: 'bundled'
            })
    ]
}
```

### Custom namespaces

Inferno always wants to deliver great performance. In order to do so, it has to make intelligent assumptions about the state of the DOM and the elements available to mutate. Custom namespaces conflict with this idea and change the schema of how different elements and attributes might work, so Inferno makes no attempt to support namespaces. Instead, SVG namespaces are automatically applied to elements and attributes based on their `tag name`.

## Development
If you want to contribute code, fork this project and submit a PR from your fork. To run browser tests you need to build the repos. A complete rebuild of the repos can take >5 mins.

```sh
$ git clone git@github.com:infernojs/inferno.git
$ cd inferno && npm i
$ npm run test:node
$ npm run build
$ npm run test:browser
```

If you only want to run the browser tests when coding, use the following to reduce turnaround by 50-80%:

```sh
$ npm run quick-test:browser # Compiles all packages and runs browser tests
$ npm run quick-test:browser-inferno # Only compiles the inferno package and runs browser tests
$ npm run quick-test:browser-debug # Compiles all packages and runs browser tests with "debug"
```

## Community

There is an InfernoJS Discord. You can join via [https://discord.gg/SUKuhgaBpF](https://discord.gg/SUKuhgaBpF).

### Contributors

This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
<a href="https://github.com/infernojs/inferno/graphs/contributors"><img src="https://opencollective.com/inferno/contributors.svg?width=890" /></a>

### Backers

Thank you to all our backers! 🙏 [[Become a backer](https://opencollective.com/inferno#backer)]

### Sponsors

Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [[Become a sponsor](https://opencollective.com/inferno#sponsor)]

Header!

Header!