react-demos: A JavaScript repository from chenyangcun

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 Demos

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/browser.min.js"></script>
  </head>
  <body>
    <div id="example"></div>
    <script type="text/babel">

      // ** Our code goes here! **

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

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. React.render() is the method which translates JSX into HTML, and renders it into the specified DOM node.

React.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 which 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.

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

React.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.

var arr = [
  <h1>Hello world!</h1>,
  <h2>React is awesome</h2>,
];
React.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.

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

React.render(
  <HelloMessage name="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.

var NotesList = React.createClass({
  render: function() {
    return (
      <ol>
      {
        this.props.children.map(function (child) {
          return <li>{child}</li>
        })
      }
      </ol>
    );
  }
});

React.render(
  <NotesList>
    <span>hello</span>
    <span>world</span>
  </NotesList>,
  document.body
);

Please be minded that only if the component has more than one child node, you could take this.props.children as an array, otherwise this.props.children.map throws a TypeError.

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 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 string.

Now we give Title a number value.

var data = 123;

React.render(
  <MyTitle title={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().

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

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

React.render(
  <MyTitle />,
  document.body
);

Demo07: Finding a DOM node (source)

Sometimes you need to reference a DOM node in a component. React gives you React.findDOMNode() to find it.

var MyComponent = React.createClass({
  handleClick: function() {
    React.findDOMNode(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>
    );
  }
});

React.render(
  <MyComponent />,
  document.getElementById('example')
);

The desired DOM node should have a ref attribute, and React.findDOMNode(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.

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>
    );
  }
});

React.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.

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>
    );
  }
});

React.render(<Input/>, document.body);

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.

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>
    );
  }
});

React.render(
  <Hello name="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.

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>
    );
  }
});

React.render(
  <UserGist source="https://api.github.com/users/octocat/gists" />,
  document.body
);

Demo12: 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 demo11 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>
    <!-- No need for Browser.js! -->
  </head>
  <body>
    <div id="example"></div>
    <script src="build/helloworld.js"></script>
  </body>
</html>

Useful links

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

License

BSD licensed

chenyangcun/react-demos