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 ofcreateElement
- 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
- Unline React, Inferno supports setting styles using string
<div style="float: left"></div>
- 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.
Migration guides
Benchmarks
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"; ;
Furthermore, Inferno also uses ES6 components like React:
import render Component from 'inferno'; { ; thisstate = counter: 0 ; } { return <div> <h1>Header!</h1> <span>Counter is at: thisstatecounter </span> </div> ; } ;
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'; { ; thisstate = counter: 0 ; } { return <div> <h1>Header!</h1> <span $></span> </div> ; } ;
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; // Start the application; // Tear down;
More Examples
If you have built something using Inferno you can add them here:
- Simple Clock (@JSFiddle)
- Simple JS Counter (@github/scorsi) : SSR Inferno (view) + Cerebral (state manager) + FuseBox (build system/bundler)
Getting Started
The easiest way to get started with Inferno is by using Create Inferno App.
Alternatively, you can try any of the following:
- the Inferno Boilerplate for a very simple setup.
- for a more advanced example demonstrating how Inferno might be used, we recommend trying out Inferno Starter Project by nightwolfz.
- for using Inferno to build a mobile app, try Inferno Mobile Starter Project by Rudy-Zidan.
- for TypeScript support and bundling with Browserify: https://github.com/smcatala/inferno-typescript-browserify-example
- for an example of how to use Inferno in codesandbox: https://codesandbox.io/s/znmyj24w4p
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/inferno@latest/dist/inferno.min.js
Or on unpkg.com:
https://unpkg.com/inferno@latest/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:
- Redux via
inferno-redux
- MobX via
inferno-mobx
- Cerebral via
@cerebral/inferno
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 legecacy string refs, use
createRef
or callbackref
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
onMouseMove
onMouseDown
onMouseUp
onSubmit
onKeyPress
onKeyDown
onKeyUp
onInput
onChange
onFocusIn
onFocusOut
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'; { props;} { return <div><input ="text" = /><div>;}
This is an example of using it with ES2015 classes:
import linkEvent Component from 'inferno'; { instance;} { return <div><input ="text" = /><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
)
; ;
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.
;; const renderer = ; // NOTE: vNodes$ represents a stream of virtual DOM node updates;
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()
;; { return } ;
Component
(package: inferno
)
Class component:
; { ... }
This is the base class for Inferno Components when they're defined using ES6 classes.
Functional component:
const MyComponent = <span>My name is: name and my age is: age</span>;
Another way of using defaultHooks.
{ return <div>1</div>;} StaticdefaultHooks = { 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
)
;
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:
;; const vNode = ; // <div class="example">Hello world!</div> ;
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')
;
createComponentVNode is used for creating vNode for Class/Functional Component.
Example:
;; { return ;} const vNode = // <div class="example">Hello Community!</div> ;
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.
;
cloneVNode
(package: inferno-clone-vnode
)
This package has same API as React.cloneElement
;
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 >children</VNode.type>
An example of using cloneVNode
:
;; const vNode = ;const newVNode = ; // we are adding an id prop to the VNode ;
If you're using JSX:
import render cloneVNode from 'inferno'; const vNode = <div ="example">Hello world</div>;const newVNode = ; // we are adding an id prop to the VNode ;
createPortal
(package: 'inferno')
HTML:
Javascript:
const render Component version createPortal from 'inferno'; { return <div>`Hello !`</div>;} const outsideDiv = document;const rootDiv = document; { return <div> Main view ... </div> ;} // render an instance of Clock into <body>:;
Results into:
Main view ... Hello Inferno!
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'; { ; // Store reference somewhere thiselement = ; // Returns object {current: null} } { return <div> <span ="span" => Ok </span> </div> ; } ;
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'; { return <div $> <Fragment ="key2"> <div>Ok</div> <span>1</span> </Fragment> </div> ;} ;
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 = ; { return <FancyButton = > Click me! </FancyButton> ; } ;
hydrate
(package: inferno-hydrate
)
; ;
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.
; options { /* 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 vNodeVNodeFlags.ContentEditable
VNodeFlags.Fragment
VNodeFlags.InUse
VnodeFlags.ForwardRef
VNodeFlags.Normalized
VNodeFlags Masks:
VNodeFlags.ForwardRefComponent
Functional component wrapped in forward refVNodeFlags.FormElement
- Is form elementVNodeFlags.Element
- Is vNode elementVNodeFlags.Component
- Is vNode ComponentVNodeFlags.DOMRef
- Bit set when vNode holds DOM referenceVNodeFlags.InUseOrNormalized
- VNode is used somewhere else or came from normalization processVNodeFlags.ClearInUseNormalized
- Opposite mask of InUse or Normalized
ChildFlags
ChildFlags.UnknownChildren
needs NormalizationChildFlags.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
)
; const string = ;
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 succesfully | |
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:
; { // [domNode] will be available for DOM nodes and components (if the component has mounted to the DOM)} { return <div>Hello world</div>;} ;
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: 'process.env': 'NODE_ENV': JSON
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 = ;
... plugins:
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 = ; ... plugins:
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
.
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]