Introduction to reactjs programing

Background knowledge

You must have knowledges as below:

  1. javascript
  2. html
  3. css

Since 2015, ES6 was geting popular, usually we are writing react.js in ES6 syntax, and it's great helpful to write high quality source code. So it's better to have knowledge of ES6.

If you don't know much about ES6, at least you must understand the ES6 keywords import, export, cause it's important for the modularized programing. Also, you must understand the AMD function require.

In this document, mostly I will show you simple source code examples, and explain how they work. You can read the source codes and try to run it. You'll understand reactjs quickly by making these simple examples clear. In the end, I list the react-router+reflux scaffold and react-router+redux scaffold source repository, it may help to start up a new project quickly.

reactjs

I would like to recommend the react offcial tutorial to start. Also, following are some simplest examples to present the basic concept.

Hello world

Following snippet is hello world scripts, you can copy that to a txt file and save it as test.html, open it via a modern browser, and see what happens.

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Hello React!</title>
    <script src="http://facebook.github.io/react/js/react.js"></script>
    <script src="http://facebook.github.io/react/js/react-dom.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.23/browser.min.js"></script>
  </head>
  <body>

    <div id="example"></div>

    <script type="text/babel">
      ReactDOM.render(<h1>Hello, world!</h1>, document.getElementById('example') );
    </script>
  </body>
</html>
Note:
  • Line 6, including the react.js library
  • Line 7, including the react-dom library
  • Line 8, including the babel compiler, which compile JSX source code to javascript code. Babel is a great tool for web frontend development
  • Line 12, a blank container div
  • Line 14, noticing the type="text/babel", it's not a regular label like type="text/javascript", that means scripts should be compiled by babel
  • Line 15, JSX scripts

Note

We'll present more examples later, the hello world html source code will be the default context html source code, you should replacing line 15 with example source code.

JSX basic

The official JSX guide JSX in Depth .

Play with jsx by following JSX scripts(replacing line 15 in example hello world with following example code).

Variable

ReactDOM.render(
    <h1>Time is&nbsp;
        <small>{new Date().toLocaleString()}</small>
    </h1>
, document.getElementById('example'))
Note:
  • the variable was wraped by {}

Style

var style = {color: '#2980B9', fontSize: '60%'};
ReactDOM.render(
    <h1>Time is&nbsp;
        <small style={style}>{new Date().toLocaleString()}</small>
    </h1>
, document.getElementById('example'))
Note:
  • variable style was wraped by {}
  • fontSize was camelCased form of font-size, it's common specification of css style

CSS class

.myFont{color: #2980B9; font-size: 60%};
ReactDOM.render(
    <h1>Time is&nbsp;
        <small className='myFont'>{new Date().toLocaleString()}</small>
    </h1>
, document.getElementById('example'))
Note:
  • className is equal with HTML attribute class

Custom attributes

If you pass properties to HTML elements that do not exist in the HTML specification, React will not render them. If you want to use a custom attribute, you should prefix it with data- or aria-.

ReactDOM.render(
    <h1>Time is&nbsp;
        <small className='myFont' data-name="william" aria-name="oneil"
               test-name="this isn't gonna be shown">
            {new Date().toLocaleString()}
        </small>
    </h1>
, document.getElementById('example'))

Component

const Timer = React.createClass({
    render: function(){
        return (
            <h1>Time is&nbsp;
                <small className='myFont' data-name="william" aria-name="oneil"
                       test-name="this isn't gonna be shown">
                    {new Date().toLocaleString()}
                </small>
            </h1>
        );
    }
});

ReactDOM.render(<Timer />, document.getElementById('example'))
Note:
  • React.createClass create a react component
  • render is predefined key function

State, properties

Refactoring source code of Component, add state and props usage example.

const TimerClock = React.createClass({
    getInitialState: function(){
        return {now: new Date().toLocaleString()}
    },
    render: function(){
        return (
            <small className='myFont' data-name="william" aria-name="oneil"
                   test-name="this isn't gonna be shown">
                {this.state.now}
            </small>
        );
    }
});

const Timer = React.createClass({
    render: function(){
        return (
            <h1>{this.props.name} is&nbsp;
                {this.props.children}
            </h1>
        )
    }
});

ReactDOM.render(
    <Timer name="Time">
        <TimerClock/>
    </Timer>
, document.getElementById('example'))
Note:
  • We have 2 components, one is TimerClock, another is Timer.
  • Timer is container of TimerClock
  • this.props.name is from line:26 name="Time", this.props.children is the reference of <TimerClock/>
  • this.state.now is from line:3 getInitialState
  • A simple conclusion: props are variables from outer scope of component, state are variables from inner scope of component

componentDidMount

Add a function componentDidMount, acting like its name, it was called when component mounted to UI page.

const TimerClock = React.createClass({
    getInitialState: function(){
        // now return null
        return {now: null}
    },
    componentDidMount: function(){
        console.log('component mounted')
        // display time in 2 seconds
        setTimeout(()=>{this.setState({now: new Date().toLocaleString()})}, 2000)
    },
    render: function(){
        return (
            <small className='myFont' data-name="william" aria-name="oneil"
                   test-name="this isn't gonna be shown">
                {this.state.now}
            </small>
        );
    }
});

const Timer = React.createClass({
    render: function(){
        return (
            <h1>{this.props.name} is&nbsp;
                {this.props.children}
            </h1>
        )
    }
});

ReactDOM.render(
    <Timer name="Time">
        <TimerClock/>
    </Timer>
, document.getElementById('example'))
Note:
  • Line 4, return now null, so when page loaed, it shows "Time is"
  • Line 6, add function componentDidMount, it's a callback after component mounted to page
  • Line 9, this.setState, only this API can modify this.state

mixins

Mixin is common use function, it's kind of like inheritence.

// add mixins source code
const IntervalMixin = {
    getInitialState: function(){
        return {intervals: []}
    },
    addInterval: function(callback){
        this.state.intervals.push(callback);
    },
    componentDidMount: function(){
        console.log('IntervalMixin loaded.');
        var intervalId = setInterval(function(){
            for(var i=0; i<this.state.intervals.length; i++){
                this.state.intervals[i]();
            }
        }.bind(this), 1000);
        this.setState({intervalId: intervalId});
    },
    componentWillUnmount: function(){
        clearInterval(this.state.intervalId);
    }
};

const TimerClock = React.createClass({
    mixins: [ IntervalMixin ],
    getInitialState: function(){
        return {now: null}
    },
    componentDidMount: function(){
        console.log('component mounted')
        // setTimeout(()=>{this.setState({now: new Date().toLocaleString()})}, 2000)
        this.addInterval(()=>{this.setState({now: new Date().toLocaleString()})});
    },
    render: function(){
        return (
            <small className='myFont' data-name="william" aria-name="oneil"
                   test-name="this isn't gonna be shown">
                {this.state.now}
            </small>
        );
    }
});

const Timer = React.createClass({
    render: function(){
        return (
            <h1>{this.props.name} is&nbsp;
                {this.props.children}
            </h1>
        )
    }
});

ReactDOM.render(
    <Timer name="Time">
        <TimerClock/>
    </Timer>
, document.getElementById('example'))
Note:
  • IntervalMixin supply a interval manager, it can be simplely call the addInterval to add interval callback, also it removes setInterval automatically when component was unmounted from page
  • Line 2, define mixin in the form of object
  • Line 3, 9, 18, getInitialState, componentDidMount, componentWillUnmount, these will be combine with class method, via configuring mixin by Line 24
  • Line 31, adding interval callback via addInterval
  • Line 10, 29, noticing the log message in console, see which componentDidMount was called first

Conclusion

You must understand concepts:
You should know that:
  • this.props was not modifiable
  • Do not modify this.state directly, always call the this.setState to change value of this.state

Setting up development environment with npm and webpack

npm

npm is depend on nodejs, installing latest nodejs, then you'll get latest npm.

For more information, https://docs.npmjs.com/

webpack

webpack is a javascript bundler, it's great helpful to modularized our javascript source code.

For more information, http://webpack.github.io/docs/what-is-webpack.html

Start a project

  1. Create a directory test, and enter the directory

  2. Add a file package.json:

    {
       "name": "test",
       "version": "0.0.0",
       "description": "",
       "scripts": {
       },
       "author": "",
       "license": "",
    }
    
  3. Run: npm install webpack webpack-dev-server webpack-hot-middleware --save-dev in terminal

  4. Run: npm install babel-core babel-loader babel-preset-react --save-dev

  5. Run: npm install babel-preset-es2015 babel-preset-react-hmre babel-register --save-dev

  6. Run: npm install react react-dom --save

  7. Notice above --save, --save-dev, those options save your installed packages to package.json

  8. Add a file webpack.config.js:

    var path = require('path');
    var webpack = require('webpack');
    
    module.exports = {
        context: path.join(__dirname, "app"),
        entry: [
            './main.jsx',
        ],
        output: {
            path: path.join(__dirname, 'dist'),
            filename: '[name].bundle.js',
            publicPath: '/static/'
        },
        plugins: [
            new webpack.optimize.OccurrenceOrderPlugin(),
            new webpack.HotModuleReplacementPlugin()
        ],
        module: {
            loaders: [
                {test: /\.jsx?$/, exclude: /node_modules/, loader: "babel", query: {presets: ['es2015', 'react']}},
                {test: /\.html$/, loader: "file?name=[name].[ext]", },
    
                {test: /\.css$/, loader: "style-loader!css-loader"},
                {test: /\.(png|jpg)$/, loader: 'url-loader?limit=8192'},
            ]
        }
    };
    
  9. Add a file index.html

    <!DOCTYPE html>
    <html>
      <head>
        <title>test</title>
      </head>
      <body>
        <div id="root">
        </div>
        <script src="/static/main.bundle.js"></script>
      </body>
    </html>
    
  10. Add a file app/main.jsx:

    import React from "react";
    import ReactDOM from "react-dom";
    
    class Test extends React.Component {
        constructor(props){
            super(props);
        }
        render(){
            return (<h1>Hello</h1>);
        }
    }
    
    ReactDOM.render(
        <Test/>, document.getElementById('root')
    );
    
  11. Directory structure:

    .
    ├── app
    │   └── main.jsx
    ├── index.html
    ├── package.json
    └── webpack.config.js
    
  12. Run: npm start, and open http://127.0.0.1:3001/

You may find the syntax in main.jsx is difference with reactjs, because here is ES6 class syntax, online tutorial for react in ES6. Both react.createClass and class do the same thing, but class in ES6 doesn't support mixins.

react-router

I recommend reading the offcial guide to learn full react-router knowledges. Here I'll show you a simple routing example to quickly start.

All examples code based on start a project.

At first, install react-router: npm install react-router --save. then clear the file main.jsx, and put following codes into it:

import React from "react";
import ReactDOM from "react-dom";

import { Route, Router, IndexRoute } from "react-router";
import { hashHistory } from "react-router";

class Page1 extends React.Component {
    constructor(props){
        super(props);
    }
    render(){
        return (<h1>Page1</h1>);
    }
}


class Page2 extends React.Component {
    constructor(props){
        super(props);
    }
    render(){
        return (<h1>Page2</h1>);
    }
}


class Page3 extends React.Component {
    constructor(props){
        super(props);
    }
    render(){
        return (<h1>Page3</h1>);
    }
}


class AppContainer extends React.Component {
    constructor(props){
        super(props);
    }
    gotoPage1(event){
        hashHistory.push('/page1');
        event.preventDefault();
    }
    gotoPage2(event){
        hashHistory.push('/page2');
        event.preventDefault();
    }
    gotoPage3(event){
        hashHistory.push('/page3');
        event.preventDefault();
    }
    render(){
        return (
            <div>
                <ul>
                    <li><a onClick={this.gotoPage1} href="">go page 1</a></li>
                    <li><a onClick={this.gotoPage2} href="">go page 2</a></li>
                    <li><a onClick={this.gotoPage3} href="">go page 3</a></li>
                </ul>
                <div>
                    {this.props.children}
                </div>
            </div>
        );
    }
}


const routes = (
    <Router history={hashHistory} >
        <Route path="/" component={AppContainer} >
            <IndexRoute component={Page1} />
            <Route path="page1" component={Page1} />
            <Route path="page2" component={Page2} />
            <Route path="page3" component={Page3} />
        </Route>
    </Router>
);


ReactDOM.render(
    routes, document.getElementById('root')
);
Notes:
  • Line 4, 5: import react-router functions, hashHistory means we use browser hash to hold the location information
  • Line 7, 17, 27: we defined 3 pages
  • Line 37: AppContainer is container of page content, Line 56: list of navigators
  • Line 62: this.props.children is page content
  • Line 70: define locations of all pages
  • Line 73: Page1 is index page

Try npm start to see the demo page.

Reflux

Reading the official guide, understanding the basic concepts action, store, view(component), after then following below simplest tutorial will make you quickly understand how reflux works.

Examples codes based on start a project.

At first, install reflux: npm install reflux --save. then clear the file main.jsx, and put following codes into it:

import React from "react";
import ReactDOM from "react-dom";

import Reflux from "reflux";


const Actions = Reflux.createActions(['loadData', 'flushData']);


const dataStore = Reflux.createStore({
    init: function(){
        this.listenTo(Actions.loadData, this.onLoadData);
        this.listenTo(Actions.flushData, this.onFlushData);
    },
    dataTemplate: JSON.stringify({
        name: '--',
        age: '--',
        status: '--'
    }),
    onLoadData: function(){
        var data = localStorage.getItem('test') || this.dataTemplate;
        this.trigger(JSON.parse(data));
    },
    onFlushData: function(params){
        var data = JSON.parse(localStorage.getItem('test') || this.dataTemplate);
        Object.assign(data, params);
        localStorage.setItem('test', JSON.stringify(data));
        Actions.loadData();
    },
    getInitialState: function(){
        return JSON.parse(localStorage.getItem('test') || this.dataTemplate);
    }
});


const TestApp = React.createClass({
    mixins: [ Reflux.connect(dataStore,"data") ],
    handleNameChange: function(event){
        Actions.flushData({"name": event.target.value});
    },
    handleAgeChange: function(event){
        Actions.flushData({"age": event.target.value});
    },
    handleStatusChange: function(event){
        Actions.flushData({"status": event.target.value});
    },
    render: function(){
        return (
            <div>
                <label>Name:</label><input onChange={this.handleNameChange} value={this.state.data.name} /><br/>
                <label>age:</label><input onChange={this.handleAgeChange} value={this.state.data.age} /><br/>
                <label>status:</label><input onChange={this.handleStatusChange} value={this.state.data.status} /><br/>
            </div>
        );
    }
});


ReactDOM.render(
    <TestApp/>, document.getElementById('root')
);

Remember that: the flow path of reflux is

╔═════════╗       ╔════════╗       ╔═════════════════╗
║ Actions ║──────>║ Stores ║──────>║ View Components ║
╚═════════╝       ╚════════╝       ╚═════════════════╝
     ^                                      │
     └──────────────────────────────────────┘

The core source structure are action/store/view.

Note:
  • As I mentioned in Start a project that component created in ES6 class way can't support mixin, and using Reflux with mixin is very convenience, so I recommend using React.createClass to create component
  • Line 4: import reflux
  • Line 7: create actions, define loadData(read)/flushData(write)
  • Line 10: create store
  • Line 12, 13: binding store and action, it's same with calling this.onLoadData when call Actions.loadData, also flushData
  • Line 11, 30: init, called when store was initialized, getInitialState, called when the store's binding component was mounted
  • Line 37, binding the store to component's state, referenced by the name data, this.state.data is coming from this.trigger in dataStore, also returned by getInitialState in dataStore

Redux

System Message: WARNING/2 (<string>, line 732); backlink

Duplicate explicit target name: "official guide".

Reading the official guide, You should understand the basic concepts action, reducer, store, component, dispatch, after then trying to run following simple example, and understanding how it works.

The redux offcial guide does not just explain to reactjs user, it was explained as a individual javascript component. So I'd like to recommend you just know the basic concepts and learn redux in reactjs by following example.

Examples codes based on start a project, and it implements the completely same input-UI with Reflux.

At first, install redux and react-redux: npm install redux react-redux --save. then clear the file main.jsx, and put following codes into it:

import React, { Component, PropTypes } from 'react';
import ReactDOM from "react-dom";

import { createStore } from 'redux';
import { connect } from 'react-redux';
import { Provider } from 'react-redux';


// create action constants
const EDIT_NAME = 'EDIT_NAME';
const EDIT_AGE = 'EDIT_AGE';
const EDIT_STATUS = 'EDIT_STATUS';

// create actions
const editName = function(text){
    return {
        type: EDIT_NAME,
        text
    };
};

const editAge = function(text){
    return {
        type: EDIT_AGE,
        text
    };
};

const editStatus = function(text){
    return {
        type: EDIT_STATUS,
        text
    };
};

// create reducers, state is { name, status, age }
const stateKey = 'test';
var initialState = {
    name: '--',
    status: '--',
    age: '--'
};
if (localStorage.getItem(stateKey) != null){
    initialState = JSON.parse(localStorage.getItem(stateKey));
}

const reducer = function(state=initialState, action){
    var data = state;
    switch(action.type){
        case EDIT_NAME:
            data = Object.assign({}, state, {"name": action.text});
            break;
        case EDIT_AGE:
            data = Object.assign({}, state, {"age": action.text});
            break;
        case EDIT_STATUS:
            data = Object.assign({}, state, {"status": action.text});
            break;
    }
    localStorage.setItem(stateKey, JSON.stringify(data));
    return data;
};

// create store
let store = createStore(reducer);

// create component
class TestApp extends React.Component{
    constructor(props){
        super(props);
    }
    handleChange(event){
        var name = event.target.name;
        var value = event.target.value;
        const { dispatch } = this.props; // same with dispatch = this.props.dispatch
        if(name == 'name'){
            dispatch(editName(value));
        }
        else if(name == 'age'){
            dispatch(editAge(value));
        }
        else if(name == 'status'){
            dispatch(editStatus(value));
        }
    }
    render(){
        const { data } = this.props;
        return (
            <div>
                <label>Name:</label><input onChange={this.handleChange.bind(this)} name="name" value={data.name} /><br/>
                <label>age:</label><input onChange={this.handleChange.bind(this)} name="age" value={data.age} /><br/>
                <label>status:</label><input onChange={this.handleChange.bind(this)} name="status" value={data.status} /><br/>
            </div>
        );
    }
}

TestApp.propTypes = {
    data: PropTypes.object.isRequired,
};

// connect store and component
const select = function(state){
    return {data: state};
};

TestApp = connect(select)(TestApp);

// render
ReactDOM.render(
    <Provider store={store}><TestApp/></Provider>,
    document.getElementById('root')
);
Note:
  • Remember the source code order, it's helpful when we start writing source code
    1. design action types
    2. create actions
    3. create reducers
    4. create store
    5. create component
    6. connect store and component
  • Line 4, 5, 6: import the shortcut functions from redux
  • Line 43, 60: persistence data
  • Line 51, 54, 57, 61: reducer always return a new state or the old state, DO NOT change it
  • Line 87: ES6 spread syntax
  • Line 98: properties validation
  • Line 107: bind the data which was returned from reducer and stored in store into component's props
  • Line 111: bind store and component via Provider

Scaffold

I create 2 scaffolds with simple source code structure, you can keep the structure and changing/adding any source files/codes to that. They are both have no animations, mixins, ets, Only the react-router, so I think it's easy to get clear with these scaffolds.

reflux, react-router

https://github.com/vincentwyshan/react-scaffold/tree/master/reflux

Repository structure:
  • actions: reflux actions
  • containers: containers(pages)
  • components: common components
  • mock: create mock data
  • stores: reflux stores
  • routes.jsx: routes
  • main.jsx: entry point

Clone the source code, run npm install and npm start to start development server.

redux, react-router

https://github.com/vincentwyshan/react-scaffold/tree/master/redux

Repository structure:
  • actions: action types and actions
  • components: common components
  • containers: containers(pages)
  • mock: create mock data
  • reducers: reducers
  • store: store configuring
  • routes.jsx: routes
  • main.jsx: entry point

Clone the source code, run npm install and npm start to start development server.

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.