How to use Webpack to develop projects-JS Tutorial-php.cn

This time I will show you how to use Webpack to develop projects, and what are the precautions for using Webpack to develop projects. The following is a practical case, let's take a look.

1. Introduction to common packaging tools

Among the packaging tools, the common ones are RequireJS, browserify, and webpack, among which RequireJS is a

JavaScriptModule loader, based on the ADM (async module define) specification implementation, browserify is a tool based on using Node.js modules in the browser, and webpack is a tool for packaging and building front-end modules. Generated tools.

2. Use of tools

(1) RequireJS as an npm package provides an executable r.js The tool is executed through the command line and is used as follows:

npm install -g requirejs
r.js -o app.build.js

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(2) The command line tool provided by browserify is used as follows:

npm install -g browserify
browserify main.js -o bundle.js

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(3) The use of webpack

As shown below, use the command to install and use it, as shown below:

npm install webpack -g
webpack main.js -o bundle.js

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In the above command line, we performed a simple global installation of webpack and packaging of the main.js file

3. Project construction

For front-end projects, webpack plays the role of a build tool, not a code dependency, and should be installed In dev-dependencies, use the following command to install:

npm install webpack --save-dev

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In this example, a simple application will be built, including two js modules

1. Generate the text "Hello world" The hello module (hello.js)

module.exports = 'Hello world';

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2. The index.js module (index.js)

var text = require('./hello');
console.log(text);

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for printing text and index.html for displaying content in the front-end browser File

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<script src="./bundle.js"></script>
</body>
</html>

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The bundle.js file introduced in the above src path does not exist because it has not been created yet. After using webpack to create the packaged js file, use the following command to create it:

webpack ./index.js bundle.js

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After executing the above command, we can see the printed results in the browsing console

Hello world

In this way, we have realized the implementation principle of a simple project , the packaged content is bundle.js, we can see the packaged content, so we won’t post the code here.

Of course, if we write code to build it like this, then it won’t be of much use. , this has to mention another advantage of webpack, that is, the use of

configuration file. Before using the configuration file, we are installing the style loader, such as the following command:

npm install style-loader css-loader --save-dev

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Through the above configuration, we can load the style

Then we set the webpack configuration file. We need to first create the webpack.config.js file under the project, the content of which is as follows:

var path = require('path');
module.exports = {
 entry: path.join(dirname, 'index'),
 output: {
  path: dirname,
  filename: 'bundle.js'
 },
 module:{
  loaders: [
   {
    test: /\.css$/,
    loaders: ['style-loader', 'css-loader']
   }
  ]
 }
};

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In the above code,

* entry: represents the
entry file of the project * output: represents the result output after building and packaging, there are still multiple items in the output object Configuration such as the output path and output file name used above
* module.loaders is the configuration used for the loader in the module. The value is an array. Each item of the array specifies a rule. The test field of the rule is
Regular expression, if the ID of the dependent module matches the regular expression, the dependency will be converted using loader. In this way, we can use the webpack command to convert the codeFor more detailed instructions, please see ( http://www.jb51.net/article/136710.htm)

The following command line command can be used to package the code

webpack

By executing the above The command can also package files, and the style can also be displayed when displaying the file. In order to prove that the style can indeed be introduced, we create the index.css file, the content of which is as follows:

body {
  background-color: darkgray;
}

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Then introduce it into the index.js we created before. The modified code is as follows:

// import style from './index.css';
var style = require('./index.css');
var text = require('./hello');
console.log(text);

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In the above code, what is commented out is the import form of the node module, and what is used is CommonJS After using the specification and using the same command to package, we can see the following effect in the browser:

That is, the style is displayed.

当然,webpack也能够通过webpack-dev-server进行项目的实时构建.
使用如下命令进行webpack-dev-server的安装:

npm install webpack-dev-server --save-dev

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在安装之后,我们能够配置使用服务器,首先,我们的package.json文件将会更为下面这样,新增内容为:

 "scripts": {
  "test": "echo \"Error: no test specified\" && exit 1",
  "start":"webpack-dev-server --inline"
 },

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在添加完这行命令之后,我们就可以使用下面命令进行启动webpack-dev-server服务器了,

npm run start

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之后完整的package.json为如下:

{
 "name": "react-basics-review",
 "version": "1.0.0",
 "description": "a practise of react study ",
 "main": "index.js",
 "scripts": {
  "test": "echo \"Error: no test specified\" && exit 1",
  "start":"webpack-dev-server --inline"
 },
 "repository": {
  "type": "git",
  "url": "git+https://github.com/suwu150/react-basics-review.git"
 },
 "author": "jkwu",
 "license": "ISC",
 "bugs": {
  "url": "https://github.com/suwu150/react-basics-review/issues"
 },
 "homepage": "https://github.com/suwu150/react-basics-review#readme",
 "devDependencies": {
  "babel-plugin-transform-object-rest-spread": "^6.23.0",
  "babel-preset-es2015": "^6.24.1",
  "css-loader": "^0.28.5",
  "lodash": "^4.17.4",
  "mocha": "^3.5.0",
  "react": "^15.6.1",
  "style-loader": "^0.18.2",
  "webpack": "^3.5.5",
  "webpack-dev-server": "^2.7.1"
 },
 "dependencies": {
  "lodash": "^4.17.4"
 }
}

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webpack配置文件修改为如下内容:

devServer中常用的配置对象属性如下：

* 1. contentBase：”./” // 本地服务器在哪个目录搭建页面，一般我们在当前目录即可；
* 2. historyApiFallback：true // 当我们搭建spa应用时非常有用，它使用的是HTML5 History Api，任意的跳转或404响应可以指向 index.html 页面；
* 3. inline：true // 用来支持dev-server自动刷新的配置，webpack有两种模式支持自动刷新，一种是iframe模式，一种是inline模式；使用iframe模式是不需要在devServer进行配置的，只需使用特定的URL格式访问即可；不过我们一般还是常用inline模式，在devServer中对inline设置为true后，当我们启动webpack-dev-server时仍要需要配置inline才能生效，这一点我们之后再说；
* 4. hot：true // 启动webpack热模块替换特性，这里也是坑最多的地方，不少博客都将hot设置了true，这里其实如果单单设置为true是不起作用,会报错误的,错误如下图所示:

这是因为在使用的过程中没有使用插件的原因,只需要将下面命令添加到配置文件即可:

plugins:[
  new webpack.HotModuleReplacementPlugin(),
 ],

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也就是调用webpack的热模块插件处理.

*5 .port：端口号(默认8080) ；
*6.其他配置信息
–quiet 控制台中不输出打包的信息
–compress 开启gzip压缩
–progress 显示打包的进度
–open 自动打开浏览器

var path = require('path');
const webpack = require ("webpack");
module.exports = {
 entry: path.join(dirname, 'index'),
 output: {
  path: dirname,
  filename: 'bundle.js',
  publicPath: "/assets/",
 },
 module:{
  loaders: [
   {
    test: /\.css$/,
    loaders: ['style-loader', 'css-loader']
   }
  ]
 },
 plugins:[
  new webpack.HotModuleReplacementPlugin(),
 ],
 devServer:{
  //我们在这里对webpack-dev-server进行配置
  contentBase: "./",
  historyApiFallback:true,
  inline:true,
  hot:true
 }
};

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index.html文件的内容修改为下面面格式:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<p>身在山中不知山高</p>
<script src="assets/bundle.js"></script>
</body>
</html>

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也就是将路径进行修改,因为在webpack.config.json文件中进行了服务器路径的配置,修改了 publicPath: "/assets/",项,在命令行执行npm run start能看到服务器正常启动,然后我们去浏览器进行访问,如下所示结果: