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Inferno is an insanely fast, 7kb React-like library for building high-performance user interfaces on both the client and server.

To quote a member of the React core team at Facebook:

Inferno 1.0 is really well written. It's how I would've rewritten React. I'd recommend reading its source to learn.

Inferno aims to provide all the great benefits that React does, plus other great features for people already familiar with the React ecosystem, such as: lifecycle events on functional components, server side render streams, better real-world performance, lower memory consumption and faster parse/load times. Furthermore, Inferno allows people to switch their existing React projects to Inferno in a few lines of code using inferno-compat.

For those not familiar with React, Inferno is a JavaScript library for building user interfaces in a declarative manner. Rather than working with MVC/MVVM style patterns, Inferno uses a component-based approach where data flows in one direction, making coding predictable, re-usable and highly testable. Based on the concept of learn once, write anywhere, Inferno doesn't impose any restrictions on how you create components. Your literally write JavaScript to state how you'd like your UI to look – Inferno does all the rest. Inferno also renders content on the server via inferno-server and NodeJS, so you can write awesome UIs that get rendered full-stack.

In terms of performance, Inferno is currently the fastest JavaScript UI library there is – both in benchmarks and actual real-world scenarios. It excels on the browser at inital page load, parse times, render times and update times. Inferno's server-side rendering is around 10-20x faster than React and Preact, it's around 5x faster than Vue and Angular2.

Summary

• Component driven + one-way data flow archietecture
• One of the fastest front-end frameworks for rendering UI in the DOM
• React-like API, concepts and component lifecycle events
• Lightweight filesize of only 7kb
• Isomorphic rendering on both client and server with inferno-server
• Highly modular with very little opinionation on how things should be done
• Unlike React and Preact, Inferno has lifecycle events on functional components
• Supports asynchronous component rendering using requestIdleCallback
• Unlike Preact and other React-like libraries, Inferno has controlled components for input/select/textarea elements

Benchmarks

• Virtual DOM Benchmark
• UI Bench
• dbmonster
• dbmonster (lazy optimisation)
• Angular Test Table
• JS Web Frameworks Benchmark - Round 4

Code Example

Let's start with some code. As you can see, Inferno intentionally keeps the same, good, 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.

import Inferno from 'inferno';

const message = "Hello world";

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

Furthermore, Inferno also uses ES6 components like React:

import Inferno from 'inferno';
import Component from 'inferno-component';

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>
    )
  }
}

Inferno.render(<MyComponent />, document.body);

More Examples

• Simple Clock (@JSFiddle)

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

Getting Started

Core package:

npm install --save inferno@beta15

Addons:

# ES2015 stateful components
npm install --save inferno-component@beta15
# server-side rendering
npm install --save inferno-server@beta15
# routing
npm install --save inferno-router@beta15

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

https://cdnjs.cloudflare.com/ajax/libs/inferno/1.0.0-beta15/inferno.min.js

Creating Virtual DOM

JSX:

npm install --save-dev babel-plugin-inferno@beta11

Hyperscript:

npm install --save inferno-hyperscript@beta15

createElement:

npm install --save inferno-create-element@beta15

Compatability with existing React apps

npm install --save-dev inferno-compat@beta15

Inferno Top-Level API

render (package: inferno)

import Inferno from 'inferno';

Inferno.render(<div />, document.body);

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 overwriten on the initial render.

createRenderer (package: inferno)

createRenderer allows for functional composition when rendering content to the DOM. An example of this is shown below:

import Inferno from 'inferno';
import { scan, map } from 'most';

...
const model$ = scan(update, 0, actions$);
const vNodes$ = map(view(actions$), model$);
const renderer = Inferno.createRenderer();
const runApp = () => scan(renderer, container, vNodes$).drain();

runApp();

createElement (package: inferno-create-element)

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

import Component from 'inferno-component';
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)
       )
    }
}

Inferno.render(createElement(BasicComponent, { title: 'abc' }), document.body);

Component (package: inferno-component)

Stateful component:

import Component from 'inferno-component';

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

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

Stateless component:

import Inferno from 'inferno';

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

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

createVNode (package: inferno)

Inferno.createVNode(
  flags,
  type,
  [props],
  [...children],
  [key],
  [ref],
  [isNormalized]
)

Create a new Inferno VNode using createVNode. A VNode is a virtual DOM object that is used to describe a single element of the UI. Typically createElement, hyperscript or JSX are used to create VNodes for Inferno, but under the hood they all use createVNode. Below is an example of using of createVNode usage:

import Inferno from 'inferno';

const vNode = Inferno.createVNode(2, 'div', { className: 'example' }, 'Hello world!');

Inferno.render(vNode, container);

The first argument for createVNode is a value from VNodeFlags, this is numerical value that used to tell Inferno what the VNode is meant to describe on the page.

cloneVNode (package: inferno)

Inferno.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 Inferno from 'inferno';

const vNode = Inferno.createVNode(2, 'div', { className: 'example' }, 'Hello world!');
const newVNode = Inferno.cloneVNode(vNode, { id: 'new' }); // we are adding an id prop to the VNode

Inferno.render(newVNode, container);

If you're using JSX:

import Inferno from 'inferno';

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

Inferno.render(newVNode, container);

findDOMNode (package: inferno)

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.

renderToString (package: inferno-server)

import Inferno from 'inferno';
import InfernoServer from 'inferno-server';

InfernoServer.renderToString(<div />);

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

Stateless component hooks

Name	Triggered when	Arguments to callback
onComponentWillMount	a stateless component is about to mount
onComponentDidMount	a stateless component has mounted successfully	domNode
onComponentWillUnmount	a stateless component is about to be unmounted	domNode
onComponentShouldUpdate	a stateless component has been triggered to updated	lastProps, nextProps
onComponentWillUpdate	a stateless component is about to perform an update	lastProps, nextProps
onComponentDidUpdate	a stateless component has performed an updated	lastProps, nextProps

Using hooks

It's simple to implicitly assign hooks to both DOM nodes and stateless components. Please note: stateful components (ES2015 classes) from inferno-component do not support hooks.

function createdCallback(domNode, props) {
    // [domNode] will be available for DOM nodes and components (if the component has mounted to the DOM)
	// [props] will only be passed for stateless components
}

Inferno.render(<div onCreated={ createdCallback } />, document.body);

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

Inferno.render(<StatelessComponent onComponentWillMount={ createdCallback } />, document.body);

Hooks provide powerful lifecycle events to stateless components, allowing you to build components without being forced to use ES2015 classes.

Third-party state libraries

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

• Redux via inferno-redux
• MobX via inferno-mobx
• Cerebral via cerebral-view-inferno

Browser Support

Inferno supports IE11+, Edge, Chrome, Firefox and Safari 8+. In order to support IE8+, Inferno requires polyfills for the following JavaScript features:

• Map object
• WeakMap object
• Object.keys
• Object.assign

Potential solutions including using the es5-shim for ES5 features and es6-shim from ES2015 features.

JSX

Inferno has its own JSX Babel plugin.

Differences from React

• Inferno is much smaller in size, 7kb vs 45kb gzip. This means Inferno is faster to transfer over the network but more imoportantly, is much faster to parse – this makes a big impact on mobile.
• Inferno is considerably faster than React. This doesn't apply to only benchmarks, but real-world applications that companies have converted to Inferno from React. Ranging from 40% - 110% performance improvement with Inferno 1.0. No other React-like library gets close to this performance gain over React.
• Inferno doesn't have a synthetic event system like React does. There are pros and cons (size and performance vs delegation and unification of browser events) to having one and we beleive that by default, using the native brownser event system is "good enough" for most apps today. We however plan on adding an add-on syntethic event system in the future to cater for those who need it.
• Inferno doesn't support React Native. Inferno was only designed for the browser/server with the DOM in mind.
• Inferno doesn't support string refs – although this can be enabled using inferno-compat. We don't recommend using them, they are the source of many memory leaks and performance issues in real-world apps. Stick with function callback refs instead.
• Inferno includes render on the main core package, rather than have a InfernoDOM package like React does. We used to do it that way, but we found people simply didn't like it given we don't support native. Furthermore, by not splitting them, we improved performance and bundle sizes.
• Inferno provides lifecycle events on stateless components. This is a major win for people who prefer lightweight components rather than bloated ES2015 classes.
• Inferno has its own devtools debugger (still in development) that differs from the React implementation. Inferno's debugger is on average, 4x faster – fixing lots of the issues with slow, laggy interfaces when developers are debugging.

Differences from Preact

• Inferno is larger in size, 7kb vs 3kb gzip. This means that Preact should parse faster than Inferno – if only slightly.
• 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 for when loading from sever-side rendered content) which means it can make drastic improvements. Unfortuantely, 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 stateless components. This is a major win for people who prefer lightweight components rather than bloated ES2015 classes.
• Inferno has its own devtools debugger (still in development) that differs from the Preact (React bound) implementation. Inferno's debugger is on average, 4x faster – fixing lots of the issues with slow, laggy interfaces when developers are debugging.
• Preact has linkState helpers built into core to help users link state to form elements. Inferno does not.

Custom namespaces

Inferno wants to always deliver great performance and 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.

The stateful ES2015 Component is located in its own package

React's ES2015 component is referenced as React.Component. To reduce the bloat on the core of Inferno, we've extracted the ES2015 component into its own package, specifically inferno-component rather than Inferno.Component. Many users are opting to use stateless components with Inferno's hooks to give similar functionality as that provided by ES2015 components.

Contributing

Testing

npm run test:browser // browser tests
npm run test:server // node tests
npm run test // browser and node tests
npm run browser // hot-loaded browser tests

Building

npm run build

Linting

npm run lint:source // lint the source

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