11 KiB
title | category | layout | ads | tags | updated | weight | |
---|---|---|---|---|---|---|---|
React.js | React | 2017/sheet | true |
|
2017-08-26 | -10 |
{%raw%}
Components
{: .-three-column}
Components
{: .-prime}
import React from 'react'
import ReactDOM from 'react-dom'
{: .-setup}
class Hello extends React.Component {
render () {
return <div className='message-box'>
Hello {this.props.name}
</div>
}
}
const el = document.body
ReactDOM.render(<Hello name='John' />, el)
Use the React.js jsfiddle to start hacking. (or the unofficial jsbin)
Properties
<Video fullscreen={true} />
{: .-setup}
render () {
this.props.fullscreen
···
}
{: data-line="2"}
Use this.props
to access properties passed to the component.
See: Properties
States
this.setState({ username: 'rstacruz' })
render () {
this.state.username
···
}
Use states (this.state
) to manage dynamic data.
See: States
Function components
function MyComponent ({ name }) {
return <div className='message-box'>
Hello {name}
</div>
}
Functional components have no state. Also, their props
are passed as the first parameter to a function.
See: Function and Class Components
Nesting
class Info extends React.Component {
render () {
const { avatar, username } = this.props
return <div>
<UserAvatar src={avatar} />
<UserProfile username={username} />
</div>
}
}
{: data-line="6,7"}
Nest components to separate concerns. See: Composing Components
Setting default props
Hello.defaultProps = {
color: 'blue'
}
See: defaultProps
Setting default state
class Hello extends React.Component {
constructor (props) {
super(props)
this.state = { visible: true }
}
}
{: data-line="4"}
Set the default state in the constructor()
.
Children
class AlertBox extends React.Component {
render () {
return <div className='alert-box'>
{this.props.children}
</div>
}
}
{: data-line="4"}
<AlertBox>
<h1>You have pending notifications</h1>
</AlertBox>
Children are passed as the children
property.
Component API
this.forceUpdate()
this.setState({ ... })
this.state
this.props
These methods and properies are available for Component
instances. See: Component API
Lifecycle
{: .-two-column}
Mounting
Method | Description |
---|---|
constructor (props) |
Before rendering # |
componentWillMount() |
Don't use this # |
render() |
Render # |
componentDidMount() |
After rendering (DOM available) # |
--- | --- |
componentWillUnmount() |
Before DOM removal # |
Set initial the state on constructor()
.
Add DOM event handlers, timers (etc) on componentDidMount()
, then remove them on componentWillUnmount()
.
Updating
Method | Description |
---|---|
componentWillReceiveProps (newProps) |
Use setState() here |
shouldComponentUpdate (newProps, newState) |
Skips render() if returns false |
componentWillUpdate (newProps, newState) |
Can't use setState() here |
render() |
Render |
componentDidUpdate (prevProps, prevState) |
Operate on the DOM here |
Called when parents change properties and .setState()
. These are not called for initial renders. See: Reference.
DOM nodes
{: .-two-column}
References
class MyComponent extends React.Component {
render () {
return <div>
<input ref={el => this.input = el} />
</div>
}
componentDidMount () {
this.input.focus()
}
}
{: data-line="4,9"}
Allows access to DOM nodes. See: Refs and the DOM
DOM Events
class MyComponent extends React.Component {
render () {
<input type="text"
value={this.state.value}
onChange={event => this.onChange(event)} />
}
onChange (event) {
this.setState({ value: event.target.vlaue })
}
}
{: data-line="5,9"}
Pass functions to attributes like onChange
. See: Events
Other features
Transfering props
<VideoPlayer src="video.mp4" />
{: .-setup}
class VideoPlayer extends React.Component {
render () {
return <VideoEmbed {...this.props} />
}
}
{: data-line="3"}
Propagates src="..."
down to the sub-component.
See Transferring props.
Top-level API
React.createClass({ ... })
React.isValidElement(c)
ReactDOM.render(<Component />, domnode, [callback])
ReactDOM.unmountComponentAtNode(domnode)
ReactDOMServer.renderToString(<Component />)
ReactDOMServer.renderToStaticMarkup(<Component />)
JSX patterns
{: .-two-column}
Style shorthand
var style = { height: 10 }
return <div style={style}></div>
return <div style={{ margin: 0, padding: 0 }}></div>
See: Inline styles
Inner HTML
function markdownify() { return "<p>...</p>"; }
<div dangerouslySetInnerHTML={{__html: markdownify()}} />
See: Dangerously set innerHTML
Lists
class TodoList extends React.Component {
render () {
const { items } = this.props
return <ul>
{items.map(item =>
<TodoItem item={item} key={item.key} />)}
</ul>
}
}
{: data-line="6,7"}
Always supply a key
property.
Conditionals
<div>
{showPopup
? <Popup />
: null}
</div>
Property validation
{: .-three-column}
PropTypes
import PropTypes from 'prop-types'
{: .-setup}
See: Typechecking with PropTypes
PropType | Description |
---|---|
any |
Anything |
--- | --- |
string |
|
number |
|
func |
Function |
bool |
True or false |
--- | --- |
oneOf (any) |
Enum types |
oneOfType (type array) |
Union |
--- | --- |
array |
|
arrayOf (...) |
|
--- | --- |
object |
|
objectOf (...) |
Object with values of a certain type |
instanceOf (...) |
Instance of a class |
shape (...) |
|
--- | --- |
element |
React element |
node |
DOM node |
--- | --- |
.isRequired |
Required |
Basic types
MyComponent.propTypes = {
email: PropTypes.string,
seats: PropTypes.number,
callback: PropTypes.func,
isClosed: PropTypes.bool,
any: PropTypes.any
}
Required types
MyCo.propTypes = {
name: PropTypes.string.isRequired
}
Elements
MyCo.propTypes = {
// React element
element: PropTypes.element,
// num, string, element, or an array of those
node: PropTypes.node
}
Enumerables (oneOf)
MyCo.propTypes = {
direction: PropTypes.oneOf([
'left', 'right'
])
}
Arrays and objects
MyCo.propTypes = {
list: PropTypes.array,
ages: PropTypes.arrayOf(PropTypes.number),
user: PropTypes.object,
user: PropTypes.objectOf(PropTypes.number),
message: PropTypes.instanceOf(Message)
}
MyCo.propTypes = {
user: PropTypes.shape({
name: PropTypes.string,
age: PropTypes.number
})
}
Use .array[Of]
, .object[Of]
, .instanceOf
, .shape
.
Custom validation
MyCo.propTypes = {
customProp: (props, key, componentName) => {
if (!/matchme/.test(props[key])) {
return new Error('Validation failed!')
}
}
}
Examples
{: .-left-reference}
Basic example
import React from 'react'
import ReactDOM from 'react-dom'
class Hello extends React.Component {
render () {
return <div className='message-box'>
Hello {this.props.name}
</div>
}
}
const el = document.body
ReactDOM.render(<Hello name='John' />, el)
Use the React.js jsfiddle to start hacking. (or the unofficial jsbin).
Try it
Open in jsbin {: target="_blank"}
Also see
{: .-one-column}
- This reference was made for React v15.
- React v0.14 cheatsheet Legacy version
- React website facebook.github.io {:.-also-see}
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