详解webpack-dev-server的简单使用

webpack-dev-server

webpack-dev-server是一个小型的Node.js Express服务器,它使用webpack-dev-middleware来服务于webpack的包,除此自外，它还有一个通过Sock.js来连接到服务器的微型运行时.

我们来看一下下面的配置文件(webpack.config.js)

var path = require("path");
module.exports = {
 entry:{
 app:["./app/main.js"]
 },
 output:{
 path:path.resolve(__dirname,"build"),
 publicPath:"/assets/",
 filename:"bundle.js"
}
}

这里你将你的源文件放在app文件夹下,并通过webpack将其打包到build文件夹下的bundle.js中.

注意:webpack-dev-server是一个独立的NPM包,你可以通过npm install webpack-dev-server来安装它.

基本目录

webpack-dev-server默认会以当前目录为基本目录,除非你制定它.

webpack-dev-server --content-base build/

上述命令是在命令行中执行的,它将build目录作为根目录.有一点需要注意的是:webpack-dev-server生成的包并没有放在你的真实目录中,而是放在了内存中.

我们在基本目录下新建一个index.html文件,然后在浏览器中输入http://localhost:8080访问.

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

自动刷新

webpack-dev-server支持两种模式来自动刷新页面.

1. iframe模式(页面放在iframe中,当发生改变时重载)
2. inline模式(将webpack-dev-sever的客户端入口添加到包(bundle)中)

两种模式都支持热模块替换(Hot Module Replacement).热模块替换的好处是只替换更新的部分,而不是页面重载.

iframe模式
使用这种模式不需要额外的配置,只需要以下面这种URL格式访问即可

http://«host»:«port»/webpack-dev-server/«path»

例如:http://localhost:8080/webpack-dev-server/index.html.

inline模式

inline模式下我们访问的URL不用发生变化,启用这种模式分两种情况:

1 当以命令行启动webpack-dev-server时,需要做两点：

1. 在命令行中添加--inline命令
2. 在webpack.config.js中添加devServer:{inline:true}

2 当以Node.js API启动webpack-dev-server时,我们也需要做两点:

1. 由于webpack-dev-server的配置中无inline选项,我们需要添加webpack-dev-server/client?http://«path»:«port»/到webpack配置的entry入口点中.
2. 将<script src="http://localhost:8080/webpack-dev-server.js"></script>添加到html文件中

 var config = require("./webpack.config.js");
 var webpack = require('webpack');
 var WebpackDevServer = require('webpack-dev-server');

config.entry.app.unshift("webpack-dev-server/client?http://localhost:8080/");

var compiler = webpack(config);
var server = new WebpackDevServer(compiler, {
 contentBase:'build/',
 publicPath: "/assets/"
});
server.listen(8080);

在Node中运行上面的代码即可。

注意：webpack配置中的devSever配置项只对在命令行模式有效。

(Hot Module Replacement)热模块替换

在命令行中运行inline模式，并启用热模块替换

这里只需要多增加 --hot指令就OK了.如下所示.

webpack-dev-server --content-base build --inline --hot

注意:命令行模式下,webpack.config.js中一定要配置output.publicPath来指定编译后的包(bundle)的访问位置.

在Nodejs API中运行inline模式，并启用热模块替换

这里需要做以下三点:

1. 在webpack.config.js的entry选项中添加:webpack/hot/dev-server
2. 在webpack.config.js的plugins选项中添加:new webpack.HotModuleReplacementPlugin()
3. 在webpack-dev-server的配置中添加：hot:true

webpack-dev-server中的配置选项

var WebpackDevServer = require("webpack-dev-server");
var webpack = require("webpack");

var compiler = webpack({
 // configuration
});
var server = new WebpackDevServer(compiler, {
 // webpack-dev-server options

 contentBase: "/path/to/directory",
 // Can also be an array, or: contentBase: "http://localhost/",

 hot: true,
 // Enable special support for Hot Module Replacement
 // Page is no longer updated, but a "webpackHotUpdate" message is send to the content
 // Use "webpack/hot/dev-server" as additional module in your entry point
 // Note: this does _not_ add the `HotModuleReplacementPlugin` like the CLI option does. 

 // Set this as true if you want to access dev server from arbitrary url.
 // This is handy if you are using a html5 router.
 historyApiFallback: false,

 // Set this if you want to enable gzip compression for assets
 compress: true,

 // Set this if you want webpack-dev-server to delegate a single path to an arbitrary server.
 // Use "**" to proxy all paths to the specified server.
 // This is useful if you want to get rid of 'http://localhost:8080/' in script[src],
 // and has many other use cases (see https://github.com/webpack/webpack-dev-server/pull/127 ).
 proxy: {
 "**": "http://localhost:9090"
 },

 setup: function(app) {
 // Here you can access the Express app object and add your own custom middleware to it.
 // For example, to define custom handlers for some paths:
 // app.get('/some/path', function(req, res) {
 // res.json({ custom: 'response' });
 // });
 },

 // pass [static options](http://expressjs.com/en/4x/api.html#express.static) to inner express server
 staticOptions: {
 },

 // webpack-dev-middleware options
 quiet: false,
 noInfo: false,
 lazy: true,
 filename: "bundle.js",
 watchOptions: {
 aggregateTimeout: 300,
 poll: 1000
 },
 // It's a required option.
 publicPath: "/assets/",
 headers: { "X-Custom-Header": "yes" },
 stats: { colors: true }
});
server.listen(8080, "localhost", function() {});
// server.close();

参考:http://webpack.github.io/docs/webpack-dev-server.html

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