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How to build a webpack microserver?

零下一度

Jun 26, 2017 pm 01:36 PM

web webpack good us

[Preface]: Because I recently used webpack’s externals when working on Baidu Map API, I discovered that I had only used webpack to do some things before. The "finishing work" after building the project - that is, packaging, without incorporating it into the "main process" of project development, is really "not making the best use of it". So here is my learning article today: Use webpack-dev-server to build a webpack server

Reference:

webpack-dev-server’s github address:

webpack1 official documentationhttp://webpack.github.io/docs/webpack-dev-server.html (It is recommended to read the document of 2)

webpack2 official document (It is recommended to read this)

Outline:

1. Review webpack Knowledge

2. Detailed explanation of the configuration properties of webpack-dev-server

3. Automatic refresh and module hot replacement of webpack-dev-server Mechanism

4. Three ways to configure the server under webpack

Review webpack Knowledge

After I simplified the directory structure, it looks like this:

My webpack.config.js:

var webpack = require('webpack')var path =require('path')
module.exports = {
entry:{
   app:path.join(__dirname,'src','index.js')
},
output:{
   filename:'bundle.js',
   path:path.join(__dirname,'dist')
  }
}

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My src/index .js:

require('./a.js')
require('./b.js')
console.log('我是index.js')

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my src/a.js:

console.log('我是a.js')

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My src/b.js:

console.log('我是b.js')

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My dist /index.html:

/*其他部分省略*/<body>  <script src="./bundle.js?1.1.11"></script></body>

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When we run the "webpack" command in the terminal, the directory becomes:

A picture to review the mechanism of webpack:

OK, let’s start building a server:

How to use it best An easy way to set up a server?

1. You need to install a module

in the terminal Enter the project directory, type npm install webpack-dev-server --save-dev and press Enter

2. Run a command in the terminal:

node_modules/.bin/webpack-dev-server(网上有的说直接输webpack-dev-server那是错的)

成功！输出的是这一段信息：

然后进入默认的localhost:8080页面：

到这里，我们要做的第一步就成功啦！

进入dist后，我们发现报了这样一段错误：

what?没有找到bundle.js?

所以我们要在webpack.config.js里写一下配置：

module.exports = {/*这里省略entry和output，参照上面写的内容*/
  devServer: {
       contentBase: path.join(__dirname, "dist")
   }
}

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保存，后打开页面看控制台，报错已经消失了！正确打印了被打包的文件内容：

详解webpack-dev-server的配置属性

1.devServer.contentBase

contentBase是我们今天要讲的第一个webpack-dev-server的配置属性，那么，contentBase做了什么事情呢？——它指定了服务器资源的根目录，如果不写入contentBase的值，那么contentBase默认是项目的目录。

在上面例子中产生错误和后来解决错误的原因：

产生错误：因为bundle.js被"放在了"我们的项目根目录里，在dist/html里此时显然不能根据路径找到bundle.js

解决错误：通过配置contentBase: path.join(__dirname, "dist")将bundle.js"放在了"dist目录下，此时bundle.js和dist/index.html位于同一目录下，通过 src="./bundle.js?1.1.11"自然就找到bundle.js了

webpack打包和webpack-dev-server开启服务的区别——

webpack输出真实的文件，而webpack-dev-server输出的文件只存在于内存中,不输出真实的文件！（注意下面两张图的区别）

webpack:当我们在终端运行"webpack"后：

webpack-dev-server:当我们在终端运行"node_modules/.bin/webpack-dev-server后：

这也就是我在上面的阐述中将bundle.js?1.1.11"放在了"加上双引号的原因

2.devServer.port

port配置属性指定了开启服务的端口号：

devServer: {
   port:7000}

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设置端口号为7000:

运行：node_modules/.bin/webpack-dev-server

这个时候就不是默认的8080的端口了，而是我们设置的7000

3.devServer.host

host设置的是服务器的主机号：

修改配置为：

devServer: {
   contentBase: path.join(__dirname, "dist"),
   port:7000,
   host:'0.0.0.0'}

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此时localhost:7000和0.0.0.0:7000都能访问成功

4.devServer.historyApiFallback

在文档里面说的很清楚，这个配置属性是用来应对返回404页面时定向到特定页面用的（the index.html page will likely have to be served in place of any 404 responses)

在dist目录下新增一个HTML页面：

/*剩下的都是很常规的HTML内容，故省略*/<p>这里是404界面</p>

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我们把webpack.config.js修改如下：

module.exports = {/*这里省略entry和output，参照上面写的内容*/devServer: {
contentBase: path.join(__dirname, "dist"),
historyApiFallback:{
   rewrites:[
      {from:/./,to:'/404.html'}
   ]
  }
 }
}

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打开页面，输入一个不存在的路由地址：

5.devServer.overlay

这个配置属性用来在编译出错的时候，在浏览器页面上显示错误，默认是false，可设置为true

首先我们人为制造一个编译错误：在我们尚未配置babel loader的项目里使用ES6写法：

在src/index.js里写入“const a”

在shell里提示编译错误：

但在浏览器里没有提示：

所以我们把webpack.config.js修改为：

module.exports = {     /*这里省略entry和output，参照上面写的内容*/
   devServer: {
       contentBase: path.join(__dirname, "dist"),
       overlay: true
   }
}

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再重新运行node_modules/.bin/webpack-dev-server，浏览器上把错误显示出来了

6.devServer.stats（字符串）

这个配置属性用来控制编译的时候shell上的输出内容，我们没有设置devServer.stats时候编译输出是这样子的：

（其中看起来有许多看似不重要的文件也被打印出来了）

stats: "errors-only"表示只打印错误：

我们把配置改成：

devServer: {
   contentBase: path.join(__dirname, "dist"),
   stats: "errors-only"}

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因为只有错误才被打印，所以，大多数信息都略过了

除此之外还有"minimal"，"normal"，"verbose"，这里不多加赘述

7.devServer.quiet

当这个配置属性和devServer.stats属于同一类型的配置属性

当它被设置为true的时候，控制台只输出第一次编译的信息，当你保存后再次编译的时候不会输出任何内容，包括错误和警告

来做个对比吧：

quiet：false（默认）：

第一次编译：

第二次编译（当你保存的时候）

quiet:true

第一次编译同上

第二次编译什么都不输出

【吐槽】这样看的话感觉这个配置好像只有负面作用呢.....

8.devServer.compress

这是一个布尔型的值，当它被设置为true的时候对所有的服务器资源采用gzip压缩

采用gzip压缩的优点和缺点：

优点：对JS，CSS资源的压缩率很高，可以极大得提高文件传输的速率，从而提升web性能

缺点：服务端要对文件进行压缩，而客户端要进行解压，增加了两边的负载

9.devServer.hot和devServer.inline

在这之前，首先要说一下的是webpack-dev-server的自动刷新和模块热替换机制

webpack-dev-server的自动刷新和模块热替换机制

这两个机制是紧紧联系在一起的

从外部角度看——自动刷新

当我们对业务代码做了一些修改然后保存后（command+s），页面会自动刷新，我们所做的修改会直接同步到页面上，而不需要我们刷新页面，或重新开启服务

（The webpack-dev-server supports multiple modes to automatically refresh the page）

从内部角度看——模块热替换

在热替换（HMR）机制里，不是重载整个页面，HMR程序会只加载被更新的那一部分模块，然后将其注入到运行中的APP中

（In Hot Module Replacement, the bundle is notified that a change happened. Rather than a full page reload, a Hot Module Replacement runtime could then load the updated modules and inject them into a running app.）

webpack-dev-server有两种模式可以实现自动刷新和模块热替换机制

1. Iframe mode(默认,无需配置)

页面被嵌入在一个iframe里面，并且在模块变化的时候重载页面

2.inline mode（需配置）添加到bundle.js中

当刷新页面的时候，一个小型的客户端被添加到webpack.config.js的入口文件中

例如在我们的例子中，在使用inline mode的热替换后，相当于入口文件从

entry:{
    app:path.join(__dirname,'src','index.js')
}

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变成了：

entry:{
    app:[path.join(__dirname,'src','index.js'),             'webpack-dev-server/client?http://localhost:8080/'  ]
}

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从一个入口变成了两个入口，并实现刷新

那怎么才能inline mode模式的刷新呢？

你需要做这些：

1在配置中写入devServer.hot：true和devServer.inline：true

2增加一个插件配置webpack.HotModuleReplacementPlugin()

例如：

var webpack = require('webpack')
module.exports = {   /*省略entry ,output等内容*/
   plugins:[new webpack.HotModuleReplacementPlugin()
    ],
   devServer: {
        inline:true,
        hot:true}
}

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打开页面：

如果有上面两行输出则表明你已经配置成功

现在还有一个问题，那就是每次直接输入node_modules/.bin/webpack-dev-server来启动服务器对我们来说简直就是莫大的痛苦，那么怎么对这一过程进行简化呢？

答案：把这个运行脚本写到package.json里就行了！

这里我把我的package.json写成：

{   "name": "webpackTest2",   "dependencies": {},   "devDependencies": {},   "scripts": {       "start": "node_modules/.bin/webpack-dev-server" }
}

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在终端运行npm start:

运行成功！

配置服务的三种方式：

1在webpack.config.js输出对象中的devServer属性中写配置（也就是我们上述所有例子的做法）

2写在package.json中，写在node 命令对应的脚本中，例如我们可以写成：

"scripts": {

"start": "node_modules/.bin/webpack-dev-server --port 8000 --inline true "

}

(但这显然并不是一个值得推荐的方式)

3使用纯node的API实现，下面是一个官方给的例子

var config = require("./webpack.config.js?1.1.11");
config.entry.app.unshift("webpack-dev-server/client?http://localhost:8080/");var compiler = webpack(config);var server = new WebpackDevServer(compiler, {       /*我们写入配置的地方*/});
server.listen(8080);

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