1 集成要点

1.1 配置技巧

1.1.1 多入口配置

Multiple entry files are allowed. It is useful for a multi-page app.

// main1.js

document.write('<h1>Hello World</h1>');

// main2.js

document.write('<h2>Hello Webpack</h2>');

index.html

<html>

<body>

</body>

</html>

webpack.config.js

module.exports ={

entry:{

bundle1: './main1.js',

bundle2: './main2.js'

output:{

filename: '[name].js'

}

};

1.1.2 CSS-loader

Demo04: CSS-loader(source)

Webpack allows you torequire CSS in JS file, then preprocessed CSS file with CSS-loader.

main.js

require('./app.css');

app.css

body{

background-color: blue;

}

index.html

<html>

<head>

</head>

<body>

<h1>Hello World</h1>

</body>

</html>

webpack.config.js

module.exports ={

entry: './main.js',

output:{

filename: 'bundle.js'

module:{

loaders:[

{ test: /\.css$/, loader: 'style-loader!css-loader'},

]

}

};

Attention, you have to use two loaders to transform CSS file. First is CSS-loader to read CSS file, and another is Style-loader to insert Style tag into HTML page. Different loaders are linked by exclamation mark(!).

After launching the server, index.html will have internal stylesheet.

<head>

body{

background-color: blue;

}

</style>

</head>

1.1.3 Imageloader

Demo05: Imageloader (source)

Webpack could also requireimages in JS files.

main.js

var img1 = document.createElement("img");

img1.src = require("./small.png");

document.body.appendChild(img1);

var img2 = document.createElement("img");

img2.src = require("./big.png");

document.body.appendChild(img2);

index.html

<html>

<body>

</body>

</html>

webpack.config.js

module.exports ={

entry: './main.js',

output:{

filename: 'bundle.js'

module:{

loaders:[

{ test: /\.(png|jpg)$/, loader: 'url-loader?limit=8192'}

]

}

};

url-loader transforms image files.If the image size is smaller than 8192 bytes, it will be transformed into DataURL; otherwise, it will be transformed into normal URL. As you see, question mark(?) is used to pass parameters into loaders.

After launching the server, small.png and big.png will have the followingURLs.

1.1.4 代码混淆插件UglifyJs Plugin

Demo07: UglifyJsPlugin (source)

Webpack has a plugin system to expand its functions. For example, UglifyJs Plugin will minify output(bundle.js) JS codes.

main.js

var longVariableName = 'Hello';

longVariableName += ' World';

document.write('<h1>'+ longVariableName +'</h1>');

index.html

<html>

<body>

</body>

</html>

webpack.config.js

var webpack = require('webpack');

var uglifyJsPlugin = webpack.optimize.UglifyJsPlugin;

module.exports ={

entry: './main.js',

output:{

filename: 'bundle.js'

plugins:[

new uglifyJsPlugin({

compress:{

warnings: false

}

})

]

};

After launching the server, main.js will be minified into following.

var o="Hello"; o+=" World", document.write("<h1>" + o + "</h1>")

1.1.5 HTMLWebpack Plugin and Open Browser Webpack Plugin

Demo08: HTML Webpack Plugin and Open Browser Webpack Plugin (source)

This demo shows you how toload 3rd-party plugins.

html-webpack-plugin could createindex.htmlforyou, and open-browser-webpack-plugin could open a new browser tab when Webpack loads.

main.js

document.write('<h1>Hello World</h1>');

webpack.config.js

var HtmlwebpackPlugin = require('html-webpack-plugin');

var OpenBrowserPlugin = require('open-browser-webpack-plugin');

module.exports ={

entry: './main.js',

output:{

filename: 'bundle.js'

plugins:[

new HtmlwebpackPlugin({

title: 'Webpack-demos',

filename: 'index.html'

}),

new OpenBrowserPlugin({

url: 'http://localhost:8080'

})

]

};

Run webpack-dev-server.

$ webpack-dev-server

Now you don't need to write index.html by hand and don't have to open browser by yourself. Webpack did all these things for you.

1.1.6 环境标记

Demo09: Environmentflags (source)

You can enable some codes only in development environment with environment flags.

main.js

document.write('<h1>Hello World</h1>');

if (__DEV__) {

document.write(new Date());

}

index.html

<html>

<body>

</body>

</html>

webpack.config.js

var webpack = require('webpack');

var devFlagPlugin = new webpack.DefinePlugin({

__DEV__ : JSON.stringify(JSON.parse(process.env.DEBUG || 'false'))

});

module.exports ={

entry: './main.js',

output:{

filename: 'bundle.js'

plugins:[devFlagPlugin]

};

Now pass environment variable into webpack.

# Linux & Mac

$ env DEBUG=true webpack-dev-server

# Windows

$ setDEBUG=true

$ webpack-dev-server

1.1.7 代码分割Code splitting

Demo10: Codesplitting (source)

For big web apps it’s not efficient to put all code into a single file, Webpack allows you to split them into several chunks. Especially if some blocks of code are only required under some circumstances, these chunks could be loaded on demand.

At first, you use require.ensure to define a split point.(official document)

// main.js

require.ensure(['./a'], function(require) {

var content = require('./a');

document.open();

document.write('<h1>' + content + '</h1>');

document.close();

});

require.ensure tells Webpack that ./a.js should be separated from bundle.js and built into a single chunk file.

// a.js

module.exports = 'Hello World';

Now Webpack takes care of the dependencies, output files and runtime stuff. You don't have to put any redundancy into your index.html and webpack.config.js.

<html>

<body>

</body>

</html>

webpack.config.js

module.exports ={

entry : './main.js',

output:{

filename : 'bundle.js'

}

};

Launch the server.

$ webpack-dev-server

On the surface, you won't feel any differences. However, Webpack actually builds main.js and a.js into different chunks(bundle.js and 1.bundle.js), and loads 1.bundle.js from bundle.js when on demand.

1.1.8 bundle-loader切割代码Code splitting with bundle-loader

Demo11: Codesplitting with bundle-loader (source)

Another way of code splitting is using bundle-loader.

// main.js

// Now a.js is requested, it will be bundled into another file

var load = require('bundle-loader!./a.js');

// To wait until a.js is available (and get the exports)

// you need to async wait for it.

load(function(file) {

document.open();

document.write('<h1>' + file + '</h1>');

document.close();

});

require('bundle-loader!./a.js') tells Webpack to load a.js from another chunk.

Now Webpack will build main.js into bundle.js, and a.js into 1.bundle.js.

1.1.9 用CommonsChunkPlugin提取通用代码块Common chunk

Demo12: Commonchunk (source)

When multi scripts have common chunks, you can extract the common part into a separate file withCommonsChunkPlugin.

// main1.jsx

var React = require('react');

var ReactDOM = require('react-dom');

ReactDOM.render(<h1>Hello World</h1>, document.getElementById('a'));

// main2.jsx

var React = require('react');

var ReactDOM = require('react-dom');

ReactDOM.render(<h2>Hello Webpack</h2>, document.getElementById('b'));

index.html

<html>

<body>

</body>

</html>

webpack.config.js

var CommonsChunkPlugin = require("webpack/lib/optimize/CommonsChunkPlugin");

module.exports ={

entry:{

bundle1: './main1.jsx',

bundle2: './main2.jsx'

output:{

filename: '[name].js'

module:{

loaders:[

{

test: /\.js[x]?$/,

loader: 'babel-loader',

query:{

presets: ['es2015', 'react']

}

]

plugins:[

new CommonsChunkPlugin('init.js')

]

}

1.1.10 第三方库代码块Vendorchunk

Demo13: Vendorchunk (source)

You can also extract the vendor libraries from a script into a separate file with CommonsChunkPlugin.

main.js

var $ = require('jquery');

$('h1').text('Hello World');

index.html

<html>

<body>

</body>

</html>

webpack.config.js

var webpack = require('webpack');

module.exports ={

entry:{

app: './main.js',

vendor: ['jquery'],

output:{

filename: 'bundle.js'

plugins:[

new webpack.optimize.CommonsChunkPlugin(/* chunkName= */'vendor', /* filename= */'vendor.js')

]

};

If you want a module available as variable in every module, such as making $ and jQuery available in every module without writing require("jquery"). You should use ProvidePlugin(Official doc).

// main.js

$('h1').text('Hello World');

// webpack.config.js

var webpack = require('webpack');

module.exports ={

entry:{

app: './main.js'

output:{

filename: 'bundle.js'

plugins:[

new webpack.ProvidePlugin({

$: "jquery",

jQuery: "jquery",

"window.jQuery": "jquery"

})

]

};

1.1.11 暴露全局变量

Demo14: Exposingglobal variables (source)

If you want to use some global variables, and don't want to include them in the Webpack bundle, you can enable externals field in webpack.config.js (official document).

For example, we have a data.js.

var data = 'Hello World';

We can expose data as a global variable.

// webpack.config.js

module.exports ={

entry: './main.jsx',

output:{

filename: 'bundle.js'

module:{

loaders:[

{

test: /\.js[x]?$/,

loader: 'babel-loader',

query:{

presets: ['es2015', 'react']

}

]

externals:{

//require('data') is external and available

// on the global var data

'data': 'data'

}

};

Now, you require data as a module variable in your script. but it actually is a global variable.

// main.jsx

var data = require('data');

var React = require('react');

var ReactDOM = require('react-dom');

ReactDOM.render(<h1>{data}</h1>,

document.body

);

1.1.12 热更新HMR

Demo15: Hot ModuleReplacement (source)

Hot Module Replacement (HMR) exchanges, adds, or removes modules while an application is running without a page reload.

You have two ways to enable Hot Module Replacement with the webpack-dev-server.

(1) Specify --hot and --inline on the command line

$ webpack-dev-server --hot --inline

Meaning of the options:

• --hot: adds the HotModuleReplacementPlugin and switch theserver to hot mode.

• --inline: embed the webpack-dev-server runtime into the bundle.

• --hot --inline: also adds the webpack/hot/dev-serverentry.

(2) Modify webpack.config.js.

• add new webpack.HotModuleReplacementPlugin() to the plugins field

• add webpack/hot/dev-server and webpack-dev-server/client?http://localhost:8080 to the entry field

webpack.config.js looks like the following.

var webpack = require('webpack');

var path = require('path');

module.exports ={

entry:[

'webpack/hot/dev-server',

'webpack-dev-server/client?http://localhost:8080',

'./index.js'

output:{

filename: 'bundle.js',

publicPath: '/static/'

plugins:[

new webpack.HotModuleReplacementPlugin()

module:{

loaders:[{

test: /\.jsx?$/,

loader: 'babel-loader',

query:{

presets: ['es2015', 'react']

include: path.join(__dirname, '.')

}]

}

};

Now launch the dev server.

$ webpack-dev-server

Visiting http://localhost:8080, you should see 'Hello World' in your browser.

Don't close the server. Open a new terminal to edit App.js, and modify 'Hello World' into 'Hello Webpack'. Save it, and see what happened in the browser.

App.js

import React, { Component } from 'react';

export default class App extends Component{

render() {

return(<h1>Hello World</h1>);

}

index.js

import React from 'react';

import ReactDOM from 'react-dom';

import App from './App';

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

index.html