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title category layout deprecated intro
React.js (v0.14)
React
2017/sheet
true
**Deprecated:** this guide targets an old version of React (v0.14). See the [updated React cheatsheet](react) for new versions.

{%raw%}

Components

var Component = React.createClass({
  render: function () {
    return <div>Hello {this.props.name}</div>;
  }
});
ReactDOM.render(<Component name="John" />, document.body);

{:.light}

Use the React.js jsfiddle to start hacking. (or the unofficial jsbin)

Nesting

var UserAvatar  = React.createClass({...});
var UserProfile = React.createClass({...});

{:.light}

var Info = React.createClass({
  render() {
    return <div>
      <UserAvatar src={this.props.avatar} />
      <UserProfile username={this.props.username} />
    </div>;
  }
});

Nest components to separate concerns. See multiple components.

States & Properties

{:.center}

States and props

<MyComponent fullscreen={true} />

{:.light}

// props
  this.props.fullscreen //=> true

// state
  this.setState({ username: 'rstacruz' });
  this.replaceState({ ... });
  this.state.username //=> 'rstacruz'
render: function () {
  return <div className={this.props.fullscreen ? 'full' : ''}>
    Welcome, {this.state.username}
  </div>;
}

Use props (this.props) to access parameters passed from the parent. Use states (this.state) to manage dynamic data.

Setting defaults

React.createClass({
  getInitialState: function () {
    return { comments: [] };
  },

  getDefaultProps: function () {
    return { name: "Hello" };
  }
);

Pre-populates this.state.comments and this.props.name.

Components

Component API

ReactDOM.findDOMNode(c)  // 0.14+
React.findDOMNode(c)  // 0.13
c.getDOMNode()        // 0.12 below

{:.light}

c.forceUpdate()
c.isMounted()

c.state
c.props

c.setState({ ... })
c.replaceState({ ... })

c.setProps({ ... })       // for deprecation
c.replaceProps({ ... })   // for deprecation

c.refs

These are methods available for Component instances. See Component API.

Component specs

Method What
render()
---- ----
getInitialState()
getDefaultProps()
---- ----
mixins: [ ... ] Mixins ... more
propTypes: { ... } Validation ... more
statics: { ... } Static methods
displayName: "..." Automatically filled by JSX
{:.greycode.no-head}

Methods and properties you can override. See component specs.

Lifecycle

Mounting

| componentWillMount() | Before rendering (no DOM yet) | | componentDidMount() | After rendering | {:.greycode.no-head.lc}

Before initial rendering occurs. Add your DOM stuff on didMount (events, timers, etc). See reference.

Updating

| componentWillReceiveProps(newProps={}) | Use setState() here | | shouldComponentUpdate(newProps={}, newState={}) | Skips render() if returns false | | componentWillUpdate(newProps={}, newState={}) | Can't use setState() here | | componentDidUpdate(prevProps={}, prevState={}) | Operate on the DOM here | {:.greycode.no-head.lc}

Called when parents change properties and .setState(). These are not called for initial renders. See reference.

Unmounting

| componentWillUnmount() | Invoked before DOM removal | {:.greycode.no-head.lc}

Clear your DOM stuff here (probably done on didMount). See reference.

Examples

Example: loading data

React.createClass({
  componentDidMount: function () {
    $.get(this.props.url, function (data) {
      this.setState(data);
    }.bind(this));
  },

  render: function () {
    return <CommentList data={this.state.data} />
  }
});

See initial AJAX data.

DOM nodes

References

<input ref="myInput">

{:.light}

this.refs.myInput
ReactDOM.findDOMNode(this.refs.myInput).focus()
ReactDOM.findDOMNode(this.refs.myInput).value

DOM Events

Add attributes like onChange. See events.

<input type="text"
    value={this.state.value}
    onChange={this.handleChange} />

{:.light}

handleChange: function(event) {
  this.setState({ value: event.target.value });
}

Allows access to DOM nodes. See References.

Two-way binding

Email: <input type="text" valueLink={this.linkState('email')} />

{:.light}

React.createClass({
  mixins: [React.addons.LinkedStateMixin]
});
this.state.email

Use LinkedStateMixin for easier two-way binding.

Property validation

Basic types

React.createClass({
  propTypes: {
    email:      React.PropTypes.string,
    seats:      React.PropTypes.number,
    settings:   React.PropTypes.object,
    callback:   React.PropTypes.func,
    isClosed:   React.PropTypes.bool,
    any:        React.PropTypes.any,
  }
});

Primitive types: .string, .number, .func, and .bool. See propTypes.

Required types

propTypes: {
  requiredFunc:  React.PropTypes.func.isRequired,
  requiredAny:   React.PropTypes.any.isRequired,

Add .isRequired.

React elements

propTypes: {
  element:  React.PropTypes.element,  // react element
  node:     React.PropTypes.node,     // num, string, element
                                      // ...or array of those

Use .element, .node.

Enumerables

propTypes: {
  enum:     React.PropTypes.oneOf(['M','F']),  // enum
  union:    React.PropTypes.oneOfType([        // any
              React.PropTypes.string,
              React.PropTypes.number ]),

Use .oneOf, .oneOfType.

Arrays and objects

propTypes: {
  array:    React.PropTypes.array,
  arrayOf:  React.PropTypes.arrayOf(React.PropTypes.number),
  object:   React.PropTypes.object,
  objectOf: React.PropTypes.objectOf(React.PropTypes.number),

  message:  React.PropTypes.instanceOf(Message),

  object2:  React.PropTypes.shape({
    color:  React.PropTypes.string,
    size:   React.PropTypes.number
  }),

Use .array[Of], .object[Of], .instanceOf, .shape.

Custom validation

propTypes: {
  customProp: function(props, propName, componentName) {
    if (!/matchme/.test(props[propName])) {
      return new Error('Validation failed!');
    }
  }
}

Supply your own function.

Other features

Class set

var cx = require('classnames');

render: function() {
  var classes = cx({
    'message': true,
    'message-important': this.props.isImportant,
    'message-read': this.props.isRead
  });

  return <div className={classes}>Great Scott!</div>;
}

Manipulate DOM classes with classnames, previously known as React.addons.classSet. See Class set.

Propagating properties

<VideoPlayer src="video.mp4" />

{:.light}

var VideoPlayer = React.createClass({
  render: function() {
    /* propagates src="..." down to this sub component */
    return <VideoEmbed {...this.props} controls='false' />;
  }
});

See Transferring props.

Mixins

var SetIntervalMixin = {
  componentWillMount: function() { .. }
}

{:.light}

var TickTock = React.createClass({
  mixins: [SetIntervalMixin]
}

See addons for some built-in mixins.

Top level API

React.createClass({ ... })

React.isValidElement(c)

ReactDOM.findDOMNode(c) // 0.14+
ReactDOM.render(<Component />, domnode, [callback]) // 0.14+
ReactDOM.unmountComponentAtNode(domnode) // 0.14+

ReactDOMServer.renderToString(<Component />) // 0.14+
ReactDOMServer.renderToStaticMarkup(<Component />) // 0.14+

JSX patterns

Style shorthand

var style = { backgroundImage: 'url(x.jpg)', height: 10 };
return <div style={style}></div>;

See inline styles.

InnerHTML

function markdownify() { return "<p>...</p>"; }
<div dangerouslySetInnerHTML={{__html: markdownify()}} />

See dangerously set innerHTML.

Lists

var TodoList = React.createClass({
  render: function() {
    function item(itemText) {
      return <li>{itemText}</li>;
    };
    return <ul>{this.props.items.map(item)}</ul>;
  }
});

See also