This is a collection of simple demos of React.js.
These demos are purposely written in a simple and clear style. You will find no difficulty in following them to learn the powerful library.
First copy the repo into your disk.
$ git clone git@github.com:ruanyf/react-demos.gitThen play with the source files under the repo's demo* directories.
<!DOCTYPE html><html><head><scriptsrc="../build/react.js"></script><scriptsrc="../build/react-dom.js"></script><scriptsrc="../build/browser.min.js"></script></head><body><divid="example"></div><scripttype="text/babel">// ** Our code goes here! **</script></body></html>- Render JSX
- Use JavaScript in JSX
- Use array in JSX
- Define a component
- this.props.children
- PropTypes
- Finding a DOM node
- this.state
- Form
- Component Lifecycle
- Ajax
- Display value from a Promise
- Server-side rendering
Demo01: Render JSX (source)
The template syntax in React is called JSX. It is allowed in JSX to put HTML tags directly into JavaScript codes. ReactDOM.render() is the method which translates JSX into HTML, and renders it into the specified DOM node.
ReactDOM.render(<h1>Hello, world!</h1>,document.getElementById('example'));Attention, you have to use <script type="text/babel"> to indicate JSX codes, and include browser.min.js, which is a browser version of Babel and could be get inside a babel-core npm release, to actually perform the transformation in the browser.
Before v0.14, React use JSTransform.js to translate <script type="text/jsx">. It has been deprecated (more info).
Demo02: Use JavaScript in JSX (source)
You could also use JavaScript in JSX. It takes angle brackets (<) as the beginning of HTML syntax, and curly brackets ({) as the beginning of JavaScript syntax.
varnames=['Alice','Emily','Kate'];ReactDOM.render(<div>{names.map(function(name){return<div>Hello, {name}!</div>})}</div>,document.getElementById('example'));Demo03: Use array in JSX (source)
If a JavaScript variable is array, JSX will implicitly concat all members of the array.
vararr=[<h1>Hello world!</h1>,<h2>React is awesome</h2>,];ReactDOM.render(<div>{arr}</div>,document.getElementById('example'));Demo04: Define a component (source)
React.createClass() creates a component class, which implements a render method to return an component instance of the class. You don't need to call new on the class in order to get an instance, just use it as a normal HTML tag.
varHelloMessage=React.createClass({render: function(){return<h1>Hello {this.props.name}</h1>;}});ReactDOM.render(<HelloMessagename="John"/>,document.getElementById('example'));Components can have attributes, and you can use this.props.[attribute] to access them, just like this.props.name of <HelloMessage name="John" /> is John.
Demo05: this.props.children (source)
React uses this.props.children to access a component's children nodes.
varNotesList=React.createClass({render: function(){return(<ol>{React.Children.map(this.props.children,function(child){return<li>{child}</li>;})}</ol>);}});ReactDOM.render(<NotesList><span>hello</span><span>world</span></NotesList>,document.body);Please be minded that the value of this.props.children has three possibilities. If the component has no children node, the value is undefined; If single children node, an object; If multiple children nodes, an array. You should be careful to handle it.
React gave us an utility React.Children for dealing with the this.props.children's opaque data structure. You could use React.Children.map to iterate this.props.children without worring its data type being undefined or object. Check official document for more methods React.Children offers.
Demo06: PropTypes (source)
Components have many specific attributes which are called ”props” in React and can be of any type.
Sometimes you need a way to validate these props. You don't want users have the freedom to input anything into your components.
React has a solution for this and it's called PropTypes.
varMyTitle=React.createClass({propTypes: {title: React.PropTypes.string.isRequired,},render: function(){return<h1>{this.props.title}</h1>;}});The above component of Mytitle has a props of title. PropTypes tells React that the title is required and its value should be string.
Now we give Title a number value.
vardata=123;ReactDOM.render(<MyTitletitle={data}/>,document.body);It means the props doesn't pass the validation, and the console will show you a error message.
Warning: Failed propType: Invalid prop `title` of type`number` supplied to `MyTitle`, expected `string`.Visit official doc for more PropTypes options.
P.S. If you want to give the props a default value, use getDefaultProps().
varMyTitle=React.createClass({getDefaultProps : function(){return{title : 'Hello World'};},render: function(){return<h1>{this.props.title}</h1>;}});ReactDOM.render(<MyTitle/>,document.body);Demo07: Finding a DOM node (source)
Sometimes you need to reference a DOM node in a component. React gives you the ref attribute to find it.
varMyComponent=React.createClass({handleClick: function(){this.refs.myTextInput.focus();},render: function(){return(<div><inputtype="text"ref="myTextInput"/><inputtype="button"value="Focus the text input"onClick={this.handleClick}/></div>);}});ReactDOM.render(<MyComponent/>,document.getElementById('example'));The desired DOM node should have a ref attribute, and this.refs.[refName] would return the corresponding DOM node. Please be minded that you could do that only after this component has been mounted into the DOM, otherwise you get null.
Demo08: this.state (source)
React thinks of component as state machines, and uses this.state to hold component's state, getInitialState() to initialize this.state(invoked before a component is mounted), this.setState() to update this.state and re-render the component.
varLikeButton=React.createClass({getInitialState: function(){return{liked: false};},handleClick: function(event){this.setState({liked: !this.state.liked});},render: function(){vartext=this.state.liked ? 'like' : 'haven\'t liked';return(<ponClick={this.handleClick}>
You {text} this. Click to toggle.
</p>);}});ReactDOM.render(<LikeButton/>,document.getElementById('example'));You could use component attributes to register event handlers, just like onClick, onKeyDown, onCopy, etc. Official Document has all supported events.
Demo09: Form (source)
According to React's design philosophy, this.state describes the state of component and is mutated via user interactions, and this.props describes the properties of component and is stable and immutable.
Since that, the value attribute of Form components, such as <input>, <textarea>, and <option>, is unaffected by any user input. If you wanted to access or update the value in response to user input, you could use the onChange event.
varInput=React.createClass({getInitialState: function(){return{value: 'Hello!'};},handleChange: function(event){this.setState({value: event.target.value});},render: function(){varvalue=this.state.value;return(<div><inputtype="text"value={value}onChange={this.handleChange}/><p>{value}</p></div>);}});ReactDOM.render(<Input/>,document.body);More information on official document.
Demo10: Component Lifecycle (source)
Components have three main parts of their lifecycle: Mounting(being inserted into the DOM), Updating(being re-rendered) and Unmounting(being removed from the DOM). React provides hooks into these lifecycle part. will methods are called right before something happens, and did methods which are called right after something happens.
varHello=React.createClass({getInitialState: function(){return{opacity: 1.0};},componentDidMount: function(){this.timer=setInterval(function(){varopacity=this.state.opacity;opacity-=.05;if(opacity<0.1){opacity=1.0;}this.setState({opacity: opacity});}.bind(this),100);},render: function(){return(<divstyle={{opacity: this.state.opacity}}>
Hello {this.props.name}</div>);}});ReactDOM.render(<Helloname="world"/>,document.body);The following is a whole list of lifecycle methods.
- componentWillMount()
- componentDidMount()
- componentWillUpdate(object nextProps, object nextState)
- componentDidUpdate(object prevProps, object prevState)
- componentWillUnmount()
- componentWillReceiveProps(object nextProps): invoked when a mounted component receives new props.
- shouldComponentUpdate(object nextProps, object nextState): invoked when a component decides whether any changes warrant an update to the DOM.
Demo11: Ajax (source)
How to get the data of a component from a server or an API provider? The answer is using Ajax to fetch data in the event handler of componentDidMount. When the server response arrives, store the data with this.setState() to trigger a re-render of your UI.
varUserGist=React.createClass({getInitialState: function(){return{username: '',lastGistUrl: ''};},componentDidMount: function(){$.get(this.props.source,function(result){varlastGist=result[0];if(this.isMounted()){this.setState({username: lastGist.owner.login,lastGistUrl: lastGist.html_url});}}.bind(this));},render: function(){return(<div>{this.state.username}'s last gist is
<ahref={this.state.lastGistUrl}>here</a>.
</div>);}});ReactDOM.render(<UserGistsource="https://api.github.com/users/octocat/gists"/>,document.body);Demo12: Display value from a Promise (source)
This demo is inspired by Nat Pryce's article "Higher Order React Components".
If a React component's data is received asynchronously, we can use a Promise object as the component's property also, just as the following.
ReactDOM.render(<RepoListpromise={$.getJSON('https://api.github.com/search/repositories?q=javascript&sort=stars')}/>,document.body);The above code takes data from Github's API, and the RepoList component gets a Promise object as its property.
Now, while the promise is pending, the component displays a loading indicator. When the promise is resolved successfully, the component displays a list of repository information. If the promise is rejected, the component displays an error message.
varRepoList=React.createClass({getInitialState: function(){return{loading: true,error: null,data: null};},componentDidMount(){this.props.promise.then(value=>this.setState({loading: false,data: value}),error=>this.setState({loading: false,error: error}));},render: function(){if(this.state.loading){return<span>Loading...</span>;}elseif(this.state.error!==null){return<span>Error: {this.state.error.message}</span>;}else{varrepos=this.state.data.items;varrepoList=repos.map(function(repo){return(<li><ahref={repo.html_url}>{repo.name}</a> ({repo.stargazers_count} stars) <br/>{repo.description}</li>);});return(<main><h1>Most Popular JavaScript Projects in Github</h1><ol>{repoList}</ol></main>);}}});Demo13: Server-side rendering (source)
This demo is copied from github.com/mhart/react-server-example, but I rewrote it with JSX syntax.
# install the dependencies in demo13 directory
$ npm install
# translate all jsx file in src subdirectory to js file
$ npm run build
# launch http server
$ node server.jsAll above demos don't use JSX compilation for clarity. In production environment, ensure to precompile JSX files before putting them online.
First, install the command-line tools Babel.
$ npm install -g babelThen precompile your JSX files(.jsx) into JavaScript(.js). Compiling the entire src directory and output it to the build directory, you may use the option --out-dir or -d.
$ babel src --out-dir buildPut the compiled JS files into HTML.
<!DOCTYPE html><html><head><title>Hello React!</title><scriptsrc="build/react.js"></script><scriptsrc="build/react-dom.js"></script><!-- No need for Browser.js! --></head><body><divid="example"></div><scriptsrc="build/helloworld.js"></script></body></html>- React's official site
- React's official examples
- React (Virtual) DOM Terminology, by Sebastian Markbåge
- The React Quick Start Guide, by Jack Callister
- Learning React.js: Getting Started and Concepts, by Ken Wheeler
- Getting started with React, by Ryan Clark
- React JS Tutorial and Guide to the Gotchas, by Justin Deal
- React Primer, by Binary Muse
- jQuery versus React.js thinking, by zigomir
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