无标题文章

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.

Related Projects

How to use

First copy the repo into your disk.

$ git clone git@github.com:ruanyf/react-demos.git

Then play with the source files under the repo's demo* directories.

HTML Template

<!DOCTYPE html>
<html>
  <head>
    <script src="../build/react.js"></script>
    <script src="../build/react-dom.js"></script>
    <script src="../build/browser.min.js"></script>
  </head>
  <body>
    <div id="example"></div>
    <script type="text/babel">

      // ** Our code goes here! **

    </script>
  </body>
</html>

Index

  1. Render JSX
  2. Use JavaScript in JSX
  3. Use array in JSX
  4. Define a component
  5. this.props.children
  6. PropTypes
  7. Finding a DOM node
  8. this.state
  9. Form
  10. Component Lifecycle
  11. Ajax
  12. Display value from a Promise
  13. Server-side rendering

Demo01: Render JSX

demo / 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@5 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

demo / 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.

var names = ['Alice', 'Emily', 'Kate'];

ReactDOM.render(
  <div>
  {
    names.map(function (name) {
      return <div>Hello, {name}!</div>
    })
  }
  </div>,
  document.getElementById('example')
);

Demo03: Use array in JSX

demo / source

If a JavaScript variable is an array, JSX will implicitly concat all members of the array.

var arr = [
  <h1>Hello world!</h1>,
  <h2>React is awesome</h2>,
];
ReactDOM.render(
  <div>{arr}</div>,
  document.getElementById('example')
);

Demo04: Define a component

demo / 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.

var HelloMessage = React.createClass({
  render: function() {
    return <h1>Hello {this.props.name}</h1>;
  }
});

ReactDOM.render(
  <HelloMessage name="John" />,
  document.getElementById('example')
);

Components would have attributes, and you can use this.props.[attribute] to access them, just like this.props.name of <HelloMessage name="John" /> is John.

Please remember the first letter of the component's name must be capitalized, otherwise React will throw an error. For instance, HelloMessage as a component's name is OK, but helloMessage is not allowed. And a React component should only have one top child node.

// wrong
var HelloMessage = React.createClass({
  render: function() {
    return <h1>
      Hello {this.props.name}
    </h1><p>
      some text
    </p>;
  }
});

// correct
var HelloMessage = React.createClass({
  render: function() {
    return <div>
      <h1>Hello {this.props.name}</h1>
      <p>some text</p>
    </div>;
  }
});

Demo05: this.props.children

demo / source

React uses this.props.children to access a component's children nodes.

var NotesList = 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.getElementById('example')
);

Please be mindful 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

demo / 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.

var MyTitle = 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 a string.

Now we give Title a number value.

var data = 123;

ReactDOM.render(
  <MyTitle title={data} />,
  document.getElementById('example')
);

It means the props doesn't pass the validation, and the console will show you an 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().

var MyTitle = React.createClass({
  getDefaultProps : function () {
    return {
      title : 'Hello World'
    };
  },

  render: function() {
     return <h1> {this.props.title} </h1>;
   }
});

ReactDOM.render(
  <MyTitle />,
  document.getElementById('example')
);

Demo07: Finding a DOM node

demo / source

Sometimes you need to reference a DOM node in a component. React gives you the ref attribute to find it.

var MyComponent = React.createClass({
  handleClick: function() {
    this.refs.myTextInput.focus();
  },
  render: function() {
    return (
      <div>
        <input type="text" ref="myTextInput" />
        <input type="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 mindful that you could do that only after this component has been mounted into the DOM, otherwise you get null.

Demo08: this.state

demo / 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.

var LikeButton = React.createClass({
  getInitialState: function() {
    return {liked: false};
  },
  handleClick: function(event) {
    this.setState({liked: !this.state.liked});
  },
  render: function() {
    var text = this.state.liked ? 'like' : 'haven\'t liked';
    return (
      <p onClick={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

demo / 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.

var Input = React.createClass({
  getInitialState: function() {
    return {value: 'Hello!'};
  },
  handleChange: function(event) {
    this.setState({value: event.target.value});
  },
  render: function () {
    var value = this.state.value;
    return (
      <div>
        <input type="text" value={value} onChange={this.handleChange} />
        <p>{value}</p>
      </div>
    );
  }
});

ReactDOM.render(<Input/>, document.getElementById('example'));

More information on official document.

Demo10: Component Lifecycle

demo / 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.

var Hello = React.createClass({
  getInitialState: function () {
    return {
      opacity: 1.0
    };
  },

  componentDidMount: function () {
    this.timer = setInterval(function () {
      var opacity = this.state.opacity;
      opacity -= .05;
      if (opacity < 0.1) {
        opacity = 1.0;
      }
      this.setState({
        opacity: opacity
      });
    }.bind(this), 100);
  },

  render: function () {
    return (
      <div style={{opacity: this.state.opacity}}>
        Hello {this.props.name}
      </div>
    );
  }
});

ReactDOM.render(
  <Hello name="world"/>,
  document.getElementById('example')
);

The following is a whole list of lifecycle methods.

  • componentWillMount(): Fired once, before initial rendering occurs. Good place to wire-up message listeners. this.setState doesn't work here.
  • componentDidMount(): Fired once, after initial rendering occurs. Can use this.getDOMNode().
  • componentWillUpdate(object nextProps, object nextState): Fired after the component's updates are made to the DOM. Can use this.getDOMNode() for updates.
  • componentDidUpdate(object prevProps, object prevState): Invoked immediately after the component's updates are flushed to the DOM. This method is not called for the initial render. Use this as an opportunity to operate on the DOM when the component has been updated.
  • componentWillUnmount(): Fired immediately before a component is unmounted from the DOM. Good place to remove message listeners or general clean up.
  • componentWillReceiveProps(object nextProps): Fired when a component is receiving new props. You might want to this.setState depending on the props.
  • shouldComponentUpdate(object nextProps, object nextState): Fired before rendering when new props or state are received. return false if you know an update isn't needed.

Demo11: Ajax

demo / 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.

var UserGist = React.createClass({
  getInitialState: function() {
    return {
      username: '',
      lastGistUrl: ''
    };
  },

  componentDidMount: function() {
    $.get(this.props.source, function(result) {
      var lastGist = 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
        <a href={this.state.lastGistUrl}>here</a>.
      </div>
    );
  }
});

ReactDOM.render(
  <UserGist source="https://api.github.com/users/octocat/gists" />,
  document.getElementById('example')
);

Demo12: Display value from a Promise

demo / 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(
  <RepoList
    promise={$.getJSON('https://api.github.com/search/repositories?q=javascript&sort=stars')}
  />,
  document.getElementById('example')
);

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.

var RepoList = 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>;
    }
    else if (this.state.error !== null) {
      return <span>Error: {this.state.error.message}</span>;
    }
    else {
      var repos = this.state.data.items;
      var repoList = repos.map(function (repo) {
        return (
          <li>
            <a href={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.js

Extras

Precompiling JSX

All 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 babel

Then 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 build

Put the compiled JS files into HTML.

<!DOCTYPE html>
<html>
  <head>
    <title>Hello React!</title>
    <script src="build/react.js"></script>
    <script src="build/react-dom.js"></script>
    <!-- No need for Browser.js! -->
  </head>
  <body>
    <div id="example"></div>
    <script src="build/helloworld.js"></script>
  </body>
</html>

Useful links

License

BSD licensed

最后编辑于 ：
©著作权归作者所有,转载或内容合作请联系作者
  • 人面猴
    序言：七十年代末，一起剥皮案震惊了整个滨河市，随后出现的几起案子，更是在滨河造成了极大的恐慌，老刑警刘岩，带你破解...
    沈念sama阅读 160,165评论 4赞 364
  • 死咒
    序言：滨河连续发生了三起死亡事件，死亡现场离奇诡异，居然都是意外死亡，警方通过查阅死者的电脑和手机，发现死者居然都...
    沈念sama阅读 67,720评论 1赞 298
  • 救了他两次的神仙让他今天三更去死
    文/潘晓璐 我一进店门，熙熙楼的掌柜王于贵愁眉苦脸地迎上来，“玉大人，你说我怎么就摊上这事。” “怎么了？”我有些...
    开封第一讲书人阅读 109,849评论 0赞 244
  • 道士缉凶录：失踪的卖姜人
    文/不坏的土叔 我叫张陵，是天一观的道长。 经常有香客问我，道长，这世上最难降的妖魔是什么？ 我笑而不...
    开封第一讲书人阅读 44,245评论 0赞 213
  • 港岛之恋（遗憾婚礼）
    正文 为了忘掉前任，我火速办了婚礼，结果婚礼上，老公的妹妹穿的比我还像新娘。我一直安慰自己，他们只是感情好，可当我...
    茶点故事阅读 52,596评论 3赞 288
  • 恶毒庶女顶嫁案：这布局不是一般人想出来的
    文/花漫 我一把揭开白布。 她就那样静静地躺着，像睡着了一般。 火红的嫁衣衬着肌肤如雪。 梳的纹丝不乱的头发上，一...
    开封第一讲书人阅读 40,747评论 1赞 222
  • 城市分裂传说
    那天，我揣着相机与录音，去河边找鬼。 笑死，一个胖子当着我的面吹牛，可吹牛的内容都是我干的。 我是一名探鬼主播，决...
    沈念sama阅读 31,977评论 2赞 315
  • 双鸳鸯连环套：你想象不到人心有多黑
    文/苍兰香墨 我猛地睁开眼，长吁一口气：“原来是场噩梦啊……” “哼！你这毒妇竟也来了？” 一声冷哼从身侧响起，我...
    开封第一讲书人阅读 30,708评论 0赞 204
  • 万荣杀人案实录
    序言：老挝万荣一对情侣失踪，失踪者是张志新（化名）和其女友刘颖，没想到半个月后，有当地人在树林里发现了一具尸体，经...
    沈念sama阅读 34,448评论 1赞 246
  • 护林员之死
    正文 独居荒郊野岭守林人离奇死亡，尸身上长有42处带血的脓包…… 初始之章·张勋 以下内容为张勋视角 年9月15日...
    茶点故事阅读 30,657评论 2赞 249
  • 白月光启示录
    正文 我和宋清朗相恋三年，在试婚纱的时候发现自己被绿了。 大学时的朋友给我发了我未婚夫和他白月光在一起吃饭的照片。...
    茶点故事阅读 32,141评论 1赞 261
  • 活死人
    序言：一个原本活蹦乱跳的男人离奇死亡，死状恐怖，灵堂内的尸体忽然破棺而出，到底是诈尸还是另有隐情，我是刑警宁泽，带...
    沈念sama阅读 28,493评论 3赞 258
  • 日本核电站爆炸内幕
    正文 年R本政府宣布，位于F岛的核电站，受9级特大地震影响，放射性物质发生泄漏。R本人自食恶果不足惜，却给世界环境...
    茶点故事阅读 33,153评论 3赞 238
  • 男人毒药：我在死后第九天来索命
    文/蒙蒙 一、第九天 我趴在偏房一处隐蔽的房顶上张望。 院中可真热闹，春花似锦、人声如沸。这庄子的主人今日做“春日...
    开封第一讲书人阅读 26,108评论 0赞 8
  • 一桩弑父案，背后竟有这般阴谋
    文/苍兰香墨 我抬头看了看天上的太阳。三九已至，却和暖如春，着一层夹袄步出监牢的瞬间，已是汗流浃背。 一阵脚步声响...
    开封第一讲书人阅读 26,890评论 0赞 198
  • 情欲美人皮
    我被黑心中介骗来泰国打工， 没想到刚下飞机就差点儿被人妖公主榨干…… 1. 我叫王不留，地道东北人。 一个月前我还...
    沈念sama阅读 35,799评论 2赞 277
  • 代替公主和亲
    正文 我出身青楼，却偏偏与公主长得像，于是被迫代替她去往敌国和亲。 传闻我的和亲对象是个残疾皇子，可洞房花烛夜当晚...
    茶点故事阅读 35,685评论 2赞 272

推荐阅读更多精彩内容