:fire: An extremely fast, React-like JavaScript library for building modern user interfaces

Last update: Jun 25, 2022

Inferno

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Inferno is an insanely fast, React-like library for building high-performance user interfaces on both the client and server.

Description

The main objective of the InfernoJS project is to provide the fastest possible runtime performance for web applications. Inferno excels at rendering real time data views or large DOM trees.

The performance is achieved through multiple optimizations, for example:

  • Inferno's own JSX plugin creates monomorphic createVNode calls, instead of createElement
  • Inferno's diff process uses bitwise flags to memoize the shape of objects
  • Child nodes are normalized only when needed
  • Special JSX flags can be used during compile time to optimize runtime performance at application level
  • Many micro optimizations

Features

  • Component driven + one-way data flow architecture
  • React-like API, concepts and component lifecycle events
  • Partial synthetic event system, normalizing events for better cross browser support
  • Inferno's linkEvent feature removes the need to use arrow functions or binding event callbacks
  • Isomorphic rendering on both client and server with inferno-server
  • Unlike React and Preact, Inferno has lifecycle events on functional components
  • Unlike Preact and other React-like libraries, Inferno has controlled components for input/select/textarea elements
  • Components can be rendered outside their current html hierarchy using createPortal - API
  • Support for older browsers without any polyfills
  • defaultHooks for Functional components, this way re-defining lifecycle events per usage can be avoided
  • Inferno supports setting styles using string <div style="background-color: red"></div> or using object literal syntax <div style={{"background-color": "red"}}></div>. For camelCase syntax support see inferno-compat.
  • Fragments (v6)
  • createRef and forwardRef APIs (v6)

Browser support

Since version 4 we have started running our test suite without any polyfills. Inferno is now part of Saucelabs open source program and we use their service for executing the tests.

InfernoJS natively supports the browsers listed below.

Build Status

Migration guides

Benchmarks

Live examples at https://infernojs.github.io/inferno

Code Example

Let's start with some code. As you can see, Inferno intentionally keeps the same design ideas as React regarding components: one-way data flow and separation of concerns.

In these examples, JSX is used via the Inferno JSX Babel Plugin to provide a simple way to express Inferno virtual DOM. You do not need to use JSX, it's completely optional, you can use hyperscript or createElement (like React does). Keep in mind that compile time optimizations are available only for JSX.

import { render } from 'inferno';

const message = "Hello world";

render(
  <MyComponent message={ message } />,
  document.getElementById("app")
);

Furthermore, Inferno also uses ES6 components like React:

import { render, Component } from 'inferno';

class MyComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      counter: 0
    };
  }
  render() {
    return (
      <div>
        <h1>Header!</h1>
        <span>Counter is at: { this.state.counter }</span>
      </div>
    );
  }
}

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

Because performance is an important aspect of this library, we want to show you how to optimize your application even further. In the example below we optimize diffing process by using JSX $HasVNodeChildren to predefine children shape compile time. Then we create text vNode using createTextVNode. All child flags are documented here.

import { createTextVNode, render, Component } from 'inferno';

class MyComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      counter: 0
    };
  }
  render() {
    return (
      <div>
        <h1>Header!</h1>
        <span $HasVNodeChildren>{createTextVNode('Counter is at: ' + this.state.counter)}</span>
      </div>
    );
  }
}

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

Tear down

To tear down inferno application you need to render null on root element. Rendering null will trigger unmount lifecycle hooks for whole vDOM tree and remove global event listeners. It is important to unmount unused vNode trees to free browser memory.

import { createTextVNode, render, Component } from 'inferno';

const rootElement = document.getElementById("app");

// Start the application
render(
  <ExampleComponent/>,
  rootElement
);

// Tear down
render(
  null,
  rootElement
);

More Examples

If you have built something using Inferno you can add them here:

Getting Started

The easiest way to get started with Inferno is by using Create Inferno App.

Alternatively, you can try any of the following:

Core package:

npm install --save inferno

Addons:

# server-side rendering
npm install --save inferno-server
# routing
npm install --save inferno-router

Pre-bundled files for browser consumption can be found on our cdnjs:

Or on jsDelivr:

https://cdn.jsdelivr.net/npm/[email protected]/dist/inferno.min.js

Or on unpkg.com:

https://unpkg.com/[email protected]/dist/inferno.min.js

Creating Virtual DOM

JSX:

npm install --save-dev babel-plugin-inferno

Hyperscript:

npm install --save inferno-hyperscript

createElement:

npm install --save inferno-create-element

Compatibility with existing React apps

npm install --save-dev inferno-compat

Note: Make sure you read more about inferno-compat before using it.

Third-party state libraries

Inferno now has bindings available for some of the major state management libraries out there:

JSX

Inferno has its own JSX Babel plugin.

Differences from React

  • Inferno doesn't have a fully synthetic event system like React does. Inferno has a partially synthetic event system, instead opting to only delegate certain events (such as onClick).
  • Inferno doesn't support React Native. Inferno was only designed for the browser/server with the DOM in mind.
  • Inferno doesn't support legacy string refs, use createRef or callback ref API
  • Inferno provides lifecycle events on functional components. This is a major win for people who prefer lightweight components rather than ES2015 classes.
  • Inferno is able to use the React Dev Tools extensions for Chrome/Firefox/etc to provide the same level of debugging experience to the Inferno user via inferno-devtools.

Differences from Preact

  • Inferno has a partial synthetic event system, resulting in better performance via delegation of certain events.
  • Inferno is much faster than Preact in rendering, updating and removing elements from the DOM. Inferno diffs against virtual DOM, rather than the real DOM (except when loading from server-side rendered content), which means it can make drastic improvements. Unfortunately, diffing against the real DOM has a 30-40% overhead cost in operations.
  • Inferno fully supports controlled components for input/select/textarea elements. This prevents lots of edgecases where the virtual DOM is not the source of truth (it should always be). Preact pushes the source of truth to the DOM itself.
  • Inferno provides lifecycle events on functional components. This is a major win for people who prefer lightweight components rather than ES2015 classes.

Event System

Like React, Inferno also uses a light-weight synthetic event system in certain places (although both event systems differ massively). Inferno's event system provides highly efficient delegation and an event helper called linkEvent.

One major difference between Inferno and React is that Inferno does not rename events or change how they work by default. Inferno only specifies that events should be camel cased, rather than lower case. Lower case events will bypass Inferno's event system in favour of using the native event system supplied by the browser. For example, when detecting changes on an <input> element, in React you'd use onChange, with Inferno you'd use onInput instead (the native DOM event is oninput).

Available synthetic events are:

  • onClick
  • onDblClick
  • onFocusIn
  • onFocusOut
  • onKeyDown
  • onKeyPress
  • onKeyUp
  • onMouseDown
  • onMouseMove
  • onMouseUp
  • onTouchEnd
  • onTouchMove
  • onTouchStart

linkEvent (package: inferno)

linkEvent() is a helper function that allows attachment of props/state/context or other data to events without needing to bind() them or use arrow functions/closures. This is extremely useful when dealing with events in functional components. Below is an example:

import { linkEvent } from 'inferno';

function handleClick(props, event) {
  props.validateValue(event.target.value);
}

function MyComponent(props) {
  return <div><input type="text" onClick={ linkEvent(props, handleClick) } /><div>;
}

This is an example of using it with ES2015 classes:

import { linkEvent, Component } from 'inferno';

function handleClick(instance, event) {
  instance.setState({ data: event.target.value });
}

class MyComponent extends Component {
  render () {
    return <div><input type="text" onClick={ linkEvent(this, handleClick) } /><div>;
  }
}

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 <input>, <textarea>, 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)

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 and Most.

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 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()

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:

import { Component } from 'inferno';

class MyComponent extends Component {
  render() {
    ...
  }
}

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

Functional component:

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

Another way of using defaultHooks.

export function Static() {
    return <div>1</div>;
}

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

Default props


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

createVNode (package: inferno)

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 VNodes for Inferno, but under the hood they all use createVNode(). Below is an example of createVNode usage:

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, 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, 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')

import { createComponentVNode } from 'inferno';

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

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

Example:

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:

flags: (number) is a value from VNodeFlags, this is a numerical value that tells Inferno what the VNode describes on the page.

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.

import { createTextVNode } from 'inferno';

createTextVNode(
  text,
  key
)

cloneVNode (package: inferno-clone-vnode)

This package has same API as React.cloneElement

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:

<VNode.type {...VNode.props} {...props}>{children}</VNode.type>

An example of using cloneVNode:

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:

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:

<div id="root"></div>
<div id="outside"></div>

Javascript:

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:

<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!

createRef (package: inferno)

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

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

childFlags: (number) is a value from ChildFlags, this tells inferno shape of the children so normalization process can be skipped.

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

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.

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)

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.

options.componentComparator ( package inferno) DEV only

This option can be used during development to create custom component comparator method. This option will be called on every Component update. It gets two parameters: lastVNode and nextVNode. When it returns true lastVNode will be replaced with nextVNode. If anything else than true is returned it falls to normal behavior.

import {options} from 'inferno';

options.componentComparator = function (lastVNode, nextVNode) {
    /* custom logic */
    return true; // Replaces lastVNode with nextVNode
}

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.Void
  • 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)

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

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

Using functional lifecycle events

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

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.

Building Inferno for use in a browser

When running Inferno on the browser using Webpack or Rollup, a replacement will need to occur during your build.

Webpack

Use the following configuration in your Webpack build for production build:

  ...
  plugins: [
    new webpack.DefinePlugin({
      'process.env': {
        'NODE_ENV': JSON.stringify('production')
      }
    })
  ]

When you are building for development, you may want to use inferno.dev.esm.js ("dev:module": "dist/index.dev.esm.js",) file. That build version has extra level of validation for development purposes. You can use it by adding following code to your webpack config.

    ...
	resolve: {
    /* When doing development workflow we want to make sure webpack picks up development build of inferno */
		alias: {
			inferno: __dirname + "/node_modules/inferno/dist/index.dev.esm.js"
		}
	}

Rollup

Use the following configuration in your Rollup build:

const replace = require('rollup-plugin-replace');
  ...
  plugins: [
    replace({
      'process.env.NODE_ENV': JSON.stringify('production'),
    })
  ]

When you are building for development, you may want to use inferno.dev.esm.js ("dev:module": "dist/index.dev.esm.js",) file. That build version has extra level of validation for development purposes. You can use it by adding following code to your rollup config.

const alias = require('@rollup/plugin-alias');

    ...
  plugins: [
    alias({
        resolve: ['.js'],
        entries: [
          {find: 'inferno', replacement: __dirname + '/node_modules/inferno/dist/index.dev.esm.js'}
        ]
    }),
  ]

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.

$ git clone [email protected]:infernojs/inferno.git
$ cd inferno && npm i
$ npm run test:node
$ npm run build
$ npm run test:browser

Community

There is an Inferno Slack. You can join via inferno-slack.herokuapp.com.

Contributors

This project exists thanks to all the people who contribute. [Contribute].

Backers

Thank you to all our backers! 🙏 [Become a backer]

Sponsors

Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [Become a sponsor]

GitHub

https://github.com/trueadm/inferno
Comments
  • 1. Inferno 3.5.0 and controlled checkboxes and radio

    Controlled inputs like type='checkbox' or type='radio' generate the onClick events but do not fire onChange events. This is my fault also, I checked the onClick only in https://github.com/AlgoTrader/inferno-controls.

    Reviewed by AlgoTrader at 2017-06-14 09:10
  • 2. styled-components not work even with inferno-compat?

    I'm using inferno-compat, last version, with styled-component and it just not render anything (with any error on console)... Did you know about this? if yes, there is any plan to make it compatible?

    I started to port my app to inferno today, so I just has no ideia if this is a bug or something already expected...

    thanks!

    Reviewed by maxguzenski at 2016-12-05 21:57
  • 3. Rendering fragments

    Or in other words, support for components to render multiple children:

    const Component = () => [<Child1 />, <Child2 />];
    

    It was said on slack it's a wanted feature with intention to be implement in future, so I'm creating this issue to have a place to track the progress.

    Someone mentioned that it was already once in Inferno, but at the cost of performance, so it was dropped until a faster implementation is discovered. Was the performance hit really that bad? Because I'd gladly take it if it means the ability to render fragments. Inferno is one of the fastest frameworks out there, so it definitely doesn't lack the perf budget.

    I consider this to be an essential feature to not have DOM polluted with useless wrapper elements which just get in the way of developing, maintaining, and styling components. And React already supports this in their Fiber rewrite, which is mostly done.

    Reviewed by darsain at 2016-12-02 10:08
  • 4. New Inferno site design suggestions/mockups

    Let's use this thread to aggregate a collection of ideas/notes and mockups for the new InfernoJS website. If you have a design you're working on submit it here for consideration.

    Reviewed by davedbase at 2016-11-19 16:18
  • 5. Make compatible with Material-UI

    Slick material design without bloat vdom library == Material-UI + InfernoJS.

    But:

    ERROR in ./~/react-addons-create-fragment/index.js
    Module not found: Error: Cannot resolve module 'inferno-compat/lib/ReactFragment' in node_modules\react-addons-create-fragment
     @ ./~/react-addons-create-fragment/index.js 1:17-51
    
    ERROR in ./~/react-addons-transition-group/index.js
    Module not found: Error: Cannot resolve module 'inferno-compat/lib/ReactTransitionGroup' in node_modules\react-addons-transition-group
     @ ./~/react-addons-transition-group/index.js 1:17-58
    

    Give me a fix or a workaround.

    Reviewed by cia48621793 at 2016-11-27 14:00
  • 6. Convert 1.0 codebase to TypeScript

    Currently the 1.0 codebase lives on the dev branch. It'll gradually be completely converted over to TS – with a keen eye on not reducing any regressions to performance. I'll need community help here (in form of PRs) to help get it all converted.

    Currently the build works fine – it handles the mix of js and ts files and also accounts for the fact that our tests need to use babel for the babel-plugin-inferno to compile JSX code. I'm struggling currently to get all this working properly – npm run test and npm run browser both fail.

    Furthermore, Inferno is using the latest [email protected] for those wondering.

    @Schnueggel any help here would be awesome :)

    Reviewed by trueadm at 2016-09-11 20:28
  • 7. patchComponent: Cannot read property '_unmounted' of null

    Observed Behaviour

    Inferno is throwing and uncaught exception Cannot read property '_unmounted' of null. It is happening inside patchComponent when lastVNode.children is null. It is throwing because instance._unmounted is null to be more specific.

    https://github.com/infernojs/inferno/blob/8a605aba148136678f1e7689064b1deb535ac1a5/packages/inferno/src/DOM/patching.ts#L289

    Expected Current Behaviour

    Inferno should not throw an uncaught exception, but should handle null as children appropriately.

    Inferno Metadata

    Using inferno/inferno-compat v1.3.0-rc.8

    macOS / Chrome

    Reviewed by kanzelm3 at 2017-02-27 21:44
  • 8. Improve the VNode normalization process

    Background

    Unlike React, Inferno's VNodes are not immutable. They are handled like pseudo-immutable objects in that if multiple instances are detected within Inferno, it attempts to clone the VNode. Inferno does this to reduce object creation and to improve performance (the dom property on VNodes constantly get updated as the mount/patch/unmount process happens during run-time).

    What we currently do

    https://github.com/trueadm/inferno/blob/master/src/core/shapes.ts#L163

    Inferno currently implements a normalization process when you call createVNode. createVNode is the main entry point into creating virtual DOM for Inferno, as such, slowing down this function can have an impact on overall app performance.

    Below explains what the normalization process currently does and what it deals with:

    1. normalizeElement if the type property is a string, but the flags pass through says "Component", Inferno tries to correctly change this a type of "Element". This is done because JSX passes over "Component" when the JSX Element starts with an uppercase name (it assumes all uppercase names are components).

    2. normalizeProps - if the props contains ref, events, children or key, usually because the VNode was created using JSX spread props, we need to put these values back onto the root of the VNode.

    3. normalizeChildren - if the VNode has children, we need to do a bunch of things here (this is generally where the performance impact comes from)

      • we need to assign a property to the children if the children is an array, in this case we assign a property $ directly to the array and set it to true. We use this to know if we've seen this array before. As Inferno's VNodes are not immutable and we use them in the mount/diffing/unmounting, we need to make sure if someone has hoisted the children array, we clone it via children.splice() so we don't mutate the same object.
      • we loop through all children, detecting if we need to flatten children (where there is an array in the children), we check if there is a string or number and convert that to a VNode and if we find a child that has dom already set, we assume it's hoisted and clone it. We do this recursively for all children within children – unless the original children does not need any changes, then we simply return the original children.
      • we do not strip invalid entries from the children or assign pseudo keys to non keyed children (like React does) based on the position of the child in the array. This means that our keyed update process is extremely fragile (see #562).

    Step 3 is causing some issues on performance. It feels like there must be a way to avoid doing this expensive cost if possible. Currently we can avoid normalization in benchmarks by specifying noNormalize via JSX or as a parameter of createVNode which takes away this cost.

    What can we do?

    We need to somehow remove normalisation. If we need to keep it, can we get away with doing it "just in time" during mounting/patching/unmounting to remove this performance loss? It's having an impact on SSR rendering where there is no DOM. It's also having an impact on animations with lots of children that have frequent updates occurring. Yes we can bypass normalization using the flag, but ideally we want to remove this altogether and have a streamlined approach. People using JSX aren't going to know how to use it properly anyway (without breaking their app).

    Any ideas on how we might improve this whilst being able to still handle mixed key children and hoisting of VNodes?

    @localvoid @thysultan @Havunen

    Reviewed by trueadm at 2016-12-12 13:44
  • 9. What is the roadmap ?

    Hi, @trueadm

    Seems great this project, but comparing to the readme. A couple of missing pieces?

    • createElement(). Is this something coming soon? I think that will give you even more stars. I was looking into the code, and shouldn't be too hard to copy from your very great t7 script? Or maybe I'm wrong.
    • different things seems unfinished inside the code, any plans for finishing this?
    • any plans for hooks ala Snabbdom? Not lifecycle, but example when you create a fragment, you can trigger a callback, same when you remove or update a fragment.
    • Server side rendring, is this going to happen soon? It's more or lest a must have if I should convert to Inferno. I'm from React world!

    Btw. Is there any benchmark for latest version, and what is the roadmap?

    I will absolutly start to use this script soon as a createElement() are done. And I like your component part too :+1:

    Reviewed by ghost at 2015-09-08 14:20
  • 10. Port React-Redux v5

    This is an initial commit for react-redux. All the code is ported except for the tests. tslint crashes on my computer in the inferno repository, so I am having problems running tests in any good way.

    Reviewed by Alxandr at 2016-12-26 12:52
  • 11. Touch events not supported?

    I am migrating a code like this from a React codebase:

    <div
    className="discover-slider"
    onTouchStart={this.onTouchStart}
    onTouchMove={this.onTouchMove}
    onTouchEnd={this.onTouchEnd}
    >
    ...
    </div>
    

    Those events are working on React but they are not being fired in Inferno. Am I doing something wrong? I think it is just not supported right now. Ideas?

    Thanks a lot for all your support guys!

    Reviewed by hguillermo at 2017-04-05 05:22
  • 12. inferno-mobx observer is incompatible with certain life cycle hooks

    Preface

    The issue comes from the fact that if class Components implement at least one of the getSnapshotBeforeUpdate or the getDerivedStateFromProps life cycle hook then the componentWillMount, componentWillReceiveProps, and componentWillUpdate hooks will be ignored.

    Which by the way this behavior is not mentioned in the documentation on class Components.

    For inferno-mobx's observer function, it uses the componentWillMount hook to set up the reactive re-rendering of the Component.

    The componentWillMount hook is normally called in createClassComponentInstance function from packages/inferno/src/DOM/utils/componentUtil.ts. But if getSnapshotBeforeUpdate or getDerivedStateFromProps are present then componentWillMount is not called.

    Observed Behaviour

    If a class Component that implements getSnapshotBeforeUpdate or getDerivedStateFromProps and is passed to inferno-mobx's observer function will not update in response to changes in the mobx observables it depends on.

    If getSnapshotBeforeUpdate and getDerivedStateFromProps are removed then things work as expected.

    Expected Current Behaviour

    A class Component passed to inferno-mobx's observer function should update in response to changes in the mobx observables it depends on regardless of which life cycle hooks it does or does not implement.

    How to Fix

    The best way (in the context of how inferno currently works) to make inferno-mobx's observer function work for class Components implementing getSnapshotBeforeUpdate or getDerivedStateFromProps is to initialize the mobx reaction on the first call of the render function. The componentDidMount could also be used, but would require forcing an update as it is called after the first use of the Component's render method. Initializing the first time render is called avoids this.

    There is one part of the componentDidMount created by inferno-mobx that may not transfer well is turning the props and state properties of the Component into mobx atoms. This is technically an unneeded step for making a Component react to changes in mobx observables. It is only needed if the value of those properties will be directly changed by user code. If props is only set by inferno and state is changed with setState (or updated when getDerivedStateFromProps is called) then the component would already be re-rendered when appropriate.

    If that aspect of inferno-mobx cannot be moved into an override of render, then to maintain backwards compatibility the observer function will need to check for getSnapshotBeforeUpdate and getDerivedStateFromProps and then override either componentDidMount or render as appropriate.

    Reviewed by Gwenio at 2021-12-16 17:07
  • 13. SSR tests are run in JSDOM env and rely on document

    Observed Behaviour

    All server rendering tests are run with JSDOM-environment exposing document which isn't available in node during SSR.

    Expected Current Behaviour

    We should run *.spec.server.jsx with separate config file and testEnvironment: "node"

    Reviewed by jhsware at 2021-10-28 07:01
  • 14. Question: migrating react app to inferno

    Hey,

    So I have a react app that I'd like to migrate to inferno for performance reasons. I spent a few hours trying to configure my (ejected) create-react-app to use inferno but wasn't successful. I was wondering if there was a guide of all the points to be careful of to do the migration? I was also wondering if it's thinkable to port an app using React hooks via xferno, described in #1453.

    Thanks.

    Reviewed by romgrk at 2021-03-15 15:30
  • 15. [inferno-test-utils] How to use this lib to change state or props, trigger change/input event/keydown event?

    When I use inferno-test-utils lib to test my inferno app, I encounter some problems that need your help. Firstly I rendered a component use renderIntoContainer.

    But I have some problems blocks my work.

    1. How to get this rendered instance that I can get the global variables bound component?
    2. How can I change state/props in a test suite so that improving code coverage?
    3. How can I manually trigger input/change events in a test suite when I test the input element?

    Look forward to your replying. Thanks.

    Reviewed by ReginaLiang at 2021-03-11 02:39
  • 16. [inferno-test-utils] renderIntoContainer can't render mocked component inner children.

    Reproduce steps:

    I have a component as follow:

    export default function TextView(props) {
      return (
        <Overlay>
          <div className={styles.container}>
            <div className={styles.header} data-l10n-id="scann-dialog-title-text" />
            <div ref={elem => props.onRef(elem)} className={styles.body}>
              {props.text}
            </div>
          </div>
        </Overlay>
      );
    }
    

    when I tested this component with jest. I mocked Overlay component.

    jest.mock("./components", () => {
      return {
        Overlay: ({ className, style, children }) => {
          return (<div id={"mockedOverlayComponent"}>{children}</div>);
        }
      };
    });
    

    then using renderIntoContainer to render TextView.

    const renderedTree = renderIntoContainer(<TextView {...props} />);

    I expect renderedTree.dom is instance of HTMLElement. Actually, renderedTree.dom is null.

    PS: But when I use render from inferno to render TextView.

    const render = require('inferno').render;
    const renderedTree = render(<TextView {...props} />, dom);
    

    the renderedTree.dom is domElement, children is correctly render, the final result is:

    <div id="mockedOverlayComponent">
        <div class="container">
            <div class="header" data-l10n-id="scann-dialog-title-text" />
            <div class="body"> testText </div>
        </div>
    </div>
    

    So, I think maybe renderIntoContainer method has some problems. Please help to deal with this issue.

    Looking forward to your reply. Thanks.

    Reviewed by ReginaLiang at 2021-03-05 07:46
  • 17. provide a esbuild workflow

    Before submitting an issue please:

    • Check that you are using the latest version of Inferno. Either using our CDN @ Master or by checking the tags on NPM.
    • Check that the bug has not been fixed in the latest development version. Use our CDN @ Edge.
    • Check that the issue has not been brought up before on Github issues.

    If you can, please distill your problem down and include a JSFiddle example for illustration. Also when requesting bug fix please include at least one test to avoid regression.

    Issue Template

    Observed Behaviour

    Inferno is...

    Expected Current Behaviour

    Inferno should...

    Inferno Metadata

    macOS / Windowx / Linux Safari / Chrome / Firefox / ...

    Reviewed by deleonio at 2020-11-06 04:46
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