react-demos

by ruanyf

ruanyf /react-demos

a collection of simple demos of React.js

15.3K Stars 6.4K Forks Last release: Not found 91 Commits 0 Releases

Available items

No Items, yet!

The developer of this repository has not created any items for sale yet. Need a bug fixed? Help with integration? A different license? Create a request here:

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 [email protected]:ruanyf/react-demos.git

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

HTML Template

<meta charset="UTF-8">
<script src="../build/react.development.js"></script>
<script src="../build/react-dom.development.js"></script>
<script src="../build/babel.min.js"></script>


<div id="example"></div>
<script type="text/babel">

  // ** Our code goes here! **

</script>

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(
  

Hello, world!

, document.getElementById('example') );

Attention, you have to use

 to indicate JSX codes, and include 
babel.min.js
, which is a browser version of Babel and could be get inside a [email protected] npm release, to actually perform the transformation in the browser.

Before v0.14, React use

JSTransform.js
to translate
. 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(

{ names.map(function (name) { return
Hello, {name}!
}) }
, 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 = [
  

Hello world!

,

React is awesome

, ]; ReactDOM.render(
{arr}
, document.getElementById('example') );

Demo04: Define a component

demo / source

class ComponentName extends React.Component
creates a component class, which implements a render method to return an component instance of the class.

Before v16.0, React use

React.createClass()
to create a component class. It has been deprecated (more info).
class HelloMessage extends React.Component {
  render() {
    return 

Hello {this.props.name}

; } }

ReactDOM.render( , document.getElementById('example') );

Components would have attributes, and you can use

this.props.[attribute]
to access them, just like
this.props.name
of
 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
class HelloMessage extends React.Component {
  render() {
    return 

Hello {this.props.name}

some text

; } }

// correct class HelloMessage extends React.Component { render() { return

Hello {this.props.name}

some text

; } }

Demo05: this.props.children

demo / source

React uses

this.props.children
to access a component's children nodes.
class NotesList extends React.Component {
  render() {
    return (
      
    { React.Children.map(this.props.children, function (child) { return
  1. {child}
  2. ; }) }
); } }

ReactDOM.render( hello world , 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.

class MyTitle extends React.Component {
  static propTypes = {
    title: PropTypes.string.isRequired,
  }
  render() {
    return 

{this.props.title}

; } }

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( , 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

defaultProps
.
class MyTitle extends React.Component {
  constructor(props) {
    super(props)
  }
  static defaultProps = {
    title: 'Hello World',
  }
  render() {
    return 

{this.props.title}

; } }

ReactDOM.render( , document.getElementById('example') );

React.PropTypes has moved into a different package since React v15.5. (more info).

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 attach a DOM node to instance created by
React.createRef()
.
class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.myTextInput = React.createRef();
    this.handleClick = this.handleClick.bind(this)
  }
  handleClick() {
    this.myTextInput.current.focus();
  }
  render() {
    return (
      
); } }

ReactDOM.render( , document.getElementById('example') );

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,
this.setState()
to update
this.state
and re-render the component.
class LikeButton extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
        liked: false
    }
    this.handleClick = this.handleClick.bind(this)
  }
  handleClick(event) {
    this.setState({ liked: !this.state.liked });
  }
  render() {
    var text = this.state.liked ? 'like' : 'haven\'t liked';
    return (
      

You {text} this. Click to toggle.

); } }

ReactDOM.render( , 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.
class Input extends React.Component {
constructor(props) {
  super(props)
  this.state = {value: 'Hello!'}
  this.handleChange = this.handleChange.bind(this)
}
handleChange(event) {
  this.setState({value: event.target.value});
}
render() {
  var value = this.state.value;
  return (
    

{value}

); } }

ReactDOM.render(, 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.
class Hello extends React.Component {
  constructor(props) {
    super(props)
    this.state = {opacity: 1.0};
  }

componentDidMount() { 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() { return (

Hello {this.props.name}
); } }

ReactDOM.render( , 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.
class UserGist extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      username: '',
      lastGistUrl: ''
    };
  }

componentDidMount() { $.get(this.props.source, function(result) { var lastGist = result[0]; this.setState({ username: lastGist.owner.login, lastGistUrl: lastGist.html_url }); }.bind(this)); }

render() { return (

{this.state.username}'s last gist is here.
); } }

ReactDOM.render( , 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(
  ,
  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.

class RepoList extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      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() { if (this.state.loading) { return Loading...; } else if (this.state.error !== null) { return Error: {this.state.error.message}; } else { var repos = this.state.data.items; var repoList = repos.map(function (repo, index) { return (

  • {repo.name} ({repo.stargazers_count} stars)
    {repo.description}
  • ); }); return (

    Most Popular JavaScript Projects in Github

      {repoList}
    ); } } }

    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.

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

    Useful links

    License

    BSD licensed

    We use cookies. If you continue to browse the site, you agree to the use of cookies. For more information on our use of cookies please see our Privacy Policy.