angular-docs-cn/aio/content/guide/webpack.md

Webpack: An Introduction

Webpack简介

Webpack is a popular module bundler, a tool for bundling application source code in convenient chunks and for loading that code from a server into a browser.

Webpack是一个广受欢迎的模块打包器， 这个工具用来把程序源码打包到一些方便易用的_块_中，以便把这些代码从服务器加载到浏览器中。

It's an excellent alternative to the SystemJS approach used elsewhere in the documentation. This guide offers a taste of Webpack and explains how to use it with Angular applications.

它是我们在文档中到处使用的SystemJS的一个优秀替代品。这篇指南会带我们尝尝Webpack的滋味，并解释如何在Angular程序中使用它。

{@a top}

You can also download the final result.

你还可以点这里下载最终结果。

{@a what-is-webpack}

What is Webpack?

什么是Webpack？

Webpack is a powerful module bundler. A bundle is a JavaScript file that incorporates assets that belong together and should be served to the client in a response to a single file request. A bundle can include JavaScript, CSS styles, HTML, and almost any other kind of file.

Webpack是一个强力的模块打包器。 所谓_包(bundle)_就是一个JavaScript文件，它把一堆_资源(assets)_合并在一起，以便它们可以在同一个文件请求中发回给客户端。 包中可以包含JavaScript、CSS样式、HTML以及很多其它类型的文件。

Webpack roams over your application source code, looking for import statements, building a dependency graph, and emitting one or more bundles. With plugins and rules, Webpack can preprocess and minify different non-JavaScript files such as TypeScript, SASS, and LESS files.

Webpack会遍历你应用中的所有源码，查找import语句，构建出依赖图谱，并产出一个(或多个)包。 通过插件和规则，Webpack可以对各种非JavaScript文件进行预处理和最小化(Minify)，比如TypeScript、SASS和LESS文件等。

You determine what Webpack does and how it does it with a JavaScript configuration file, webpack.config.js.

我们通过一个JavaScript配置文件webpack.config.js来决定Webpack做什么以及如何做。

{@a entries-outputs}

Entries and outputs

入口与输出

You supply Webpack with one or more entry files and let it find and incorporate the dependencies that radiate from those entries. The one entry point file in this example is the application's root file, src/main.ts:

我们给Webpack提供一个或多个入口文件，来让它查找与合并那些从这些入口点发散出去的依赖。 在下面这个例子中，我们的入口点是该应用的根文件src/app.ts：

Webpack inspects that file and traverses its import dependencies recursively.

Webpack探查那个文件，并且递归遍历它的import依赖。

It sees that you're importing @angular/core so it adds that to its dependency list for potential inclusion in the bundle. It opens the @angular/core file and follows its network of import statements until it has built the complete dependency graph from main.ts down.

这里，Webpack看到我们正在导入@angular/core，于是就这个文件加入到它的依赖列表里，为(有可能)把该文件打进包中做准备。 它打开@angular/core并追踪由_该文件的_import语句构成的网络，直到构建出从main.ts往下的整个依赖图谱。

Then it outputs these files to the app.js bundle file designated in configuration:

然后它把这些文件输出到当前配置所指定的_包文件_app.js中：

output: { filename: 'app.js' }

This app.js output bundle is a single JavaScript file that contains the application source and its dependencies. You'll load it later with a <script> tag in the index.html.

这个app.js输出包是个单一的JavaScript文件，它包含程序的源码及其所有依赖。 后面我们将在index.html中用<script>标签来加载它。

{@a multiple-bundles}

Multiple bundles

多重包

You probably don't want one giant bundle of everything. It's preferable to separate the volatile application app code from comparatively stable vendor code modules.

我们可能不会希望把所有东西打进一个巨型包，而更喜欢把多变的应用代码从相对稳定的第三方提供商模块中分离出来。

Change the configuration so that it has two entry points, main.ts and vendor.ts:

所以要修改配置，以获得两个入口点：main.ts和vendor.ts：

entry: { app: 'src/app.ts', vendor: 'src/vendor.ts' },

output: { filename: '[name].js' }

Webpack constructs two separate dependency graphs and emits two bundle files, one called app.js containing only the application code and another called vendor.js with all the vendor dependencies.

Webpack会构造出两个独立的依赖图谱，并产出两个包文件：一个叫做app.js，它只包含我们的应用代码；另一个叫做vendor.js，它包含所有的提供商依赖。

The [name] in the output name is a placeholder that a Webpack plugin replaces with the entry names, app and vendor. Plugins are covered later in the guide.

在输出文件名中出现的[name]是一个Webpack的占位符，它将被一个Webpack插件替换为入口点的名字，分别是app和vendor。插件在本章的稍后部分讲解。

To tell Webpack what belongs in the vendor bundle, add a vendor.ts file that only imports the application's third-party modules:

要想告诉Webpack哪些文件属于vendor包，可以添加一个vendor.ts文件，它只导入该应用的第三方模块：

{@a loaders}

Loaders

加载器(Loader)

Webpack can bundle any kind of file: JavaScript, TypeScript, CSS, SASS, LESS, images, HTML, fonts, whatever. Webpack itself only understands JavaScript files. Teach it to transform non-JavaScript file into their JavaScript equivalents with loaders. Configure loaders for TypeScript and CSS as follows.

Webpack可以打包任何类型的文件：JavaScript、TypeScript、CSS、SASS、LESS、图片、HTML以及字体文件等等。 但Webpack本身只认识JavaScript文件。 我们要通过加载器来告诉它如何把这些文件处理成JavaScript文件。 在这里，我们为TypeScript和CSS文件配置了加载器。

rules: [ { test: /\.ts$/, loader: 'awesome-typescript-loader' }, { test: /\.css$/, loaders: 'style-loader!css-loader' } ]

When Webpack encounters import statements like the following, it applies the test RegEx patterns.

当Webpack遇到如下所示的import语句时，它就会调用正则表达式的test方法。

import { AppComponent } from './app.component.ts';

import 'uiframework/dist/uiframework.css';

When a pattern matches the filename, Webpack processes the file with the associated loader.

如果一个模式匹配上文件名，Webpack就用它所关联的加载器处理这个文件。

The first import file matches the .ts pattern so Webpack processes it with the awesome-typescript-loader. The imported file doesn't match the second pattern so its loader is ignored.

第一个import文件匹配上了.ts模式，于是Webpack就用awesome-typescript-loader加载器处理它。 导入的文件没有匹配上第二个模式，于是它的加载器就被忽略了。

The second import matches the second .css pattern for which you have two loaders chained by the (!) character. Webpack applies chained loaders right to left . So it applies the css loader first to flatten CSS @import and url(...) statements. Then it applies the style loader to append the css inside <style> elements on the page.

第二个import匹配上了第二个.css模式，它有两个用叹号字符(!)串联起来的加载器。 Webpack会从右到左逐个应用串联的加载器，于是它先应用了css加载器(用来平面化CSS的@import和url(...)语句)， 然后应用了style加载器(用来把css追加到页面上的*<style>*元素中)。

{@a plugins}

Plugins

插件

Webpack has a build pipeline with well-defined phases. Tap into that pipeline with plugins such as the uglify minification plugin:

Webpack有一条构建流水线，它被划分成多个经过精心定义的阶段(phase)。 我们可以把插件(比如uglify代码最小化插件)挂到流水线上：

plugins: [ new webpack.optimize.UglifyJsPlugin() ]

{@a configure-webpack}

Configuring Webpack

配置Webpack

After that brief orientation, you are ready to build your own Webpack configuration for Angular apps.

经过简短的培训之后，我们准备为Angular应用构建一份自己的Webpack配置了。

Begin by setting up the development environment.

从设置开发环境开始。

Create a new project folder.

创建一个新的项目文件夹。

mkdir angular-webpack cd angular-webpack

Add these files :

把下列文件添加到根目录下：

Many of these files should be familiar from other Angular documentation guides, especially the Typescript configuration and npm packages guides.

这些文件很多都很眼熟，它们在其他文档里已经出现过，特别是TypeScript配置和npm包这两章里。

Webpack, the plugins, and the loaders are also installed as packages. They are listed in the updated packages.json.

Webpack，包括它的插件以及加载器，也是以npm包的形式安装的，它们也列在了修改后的 package.json 中。

Open a terminal window and install the npm packages.

打开命令行窗口并安装这些npm包

npm install

{@a polyfills}

Polyfills

You'll need polyfills to run an Angular application in most browsers as explained in the Browser Support guide.

我们在浏览器支持章节里解释过，Angular应用要能在大多数的浏览器里运行，它还需要一些polyfills。

Polyfills should be bundled separately from the application and vendor bundles. Add a polyfills.ts like this one to the src/ folder.

Polyfills最好跟应用代码和vendor代码区分开来单独打包，所以我们需要在src/文件夹里添加一个polyfills.ts文件，代码如下：

Loading polyfills

Load zone.js early within polyfills.ts, immediately after the other ES6 and metadata shims.

polyfills.ts文件里，zone.js库须尽早引入，紧跟在ES6 shims和metadata shims之后。

Because this bundle file will load first, polyfills.ts is also a good place to configure the browser environment for production or development.

由于这个包最先加载，所以polyfills.ts非常适合用来配置浏览器环境，如生产环境配置或是开发环境。

{@a common-configuration}

Common configuration

通用配置

Developers typically have separate configurations for development, production, and test environments. All three have a lot of configuration in common.

开发、生产、测试等不同的环境通常会分开配置，但实际上这些配置也有很多地方是通用的。

Gather the common configuration in a file called webpack.common.js.

我们可以把这些通用的配置收归到一个文件，命名为webpack.common.js。

{@a inside-webpack-commonjs}

Inside webpack.common.js

webpack.common.js解读

Webpack is a NodeJS-based tool that reads configuration from a JavaScript commonjs module file.

Webpack是基于NodeJS的一个工具，它能够从一个commonjs规范的JavaScript模块文件里读取配置。

The configuration imports dependencies with require statements and exports several objects as properties of a module.exports object.

这个配置文件是通过require语句导入依赖，然后将多个对象作为module.exports对象的属性导出。

• entry—the entry-point files that define the bundles.

  entries - 包体的入口文件。

• resolve—how to resolve file names when they lack extensions.

  resolve - 省略扩展名时如何解释文件名。

• module.rules— module is an object with rules for deciding how files are loaded.

  module.rules - module是一个对象，里面的rules属性用来决定文件如何加载。

• plugins—creates instances of the plugins.

  plugins - 创建插件的实例。

{@a common-entries}

entry

The first export is the entry object:

如上所述，第一个导出的对象是entries：

This entry object defines the three bundles:

entry对象定义了三个包：

• polyfills—the polyfills needed to run Angular applications in most modern browsers.

  polyfills - 使得Angular应用能够运行在大多数的现代浏览器。

• vendor—the third-party dependencies such as Angular, lodash, and bootstrap.css.

  vendor - 第三方依赖，如Angular、lodash和bootstrap.css。

• app—the application code.

  app - 应用代码。

{@a common-resolves}

resolve extension-less imports

resolve 无扩展名的文件导入

The app will import dozens if not hundreds of JavaScript and TypeScript files. You could write import statements with explicit extensions like this example:

如果你的应用程序只须import几十个JavaScript或TypeScript文件，而不是几百个，你可以在import语句里完整写上扩展名，如：

import { AppComponent } from './app.component.ts';

But most import statements don't mention the extension at all. Tell Webpack to resolve extension-less file requests by looking for matching files with .ts extension or .js extension (for regular JavaScript files and pre-compiled TypeScript files).

但实际上大部分import语句都不带扩展名，我们可以告诉Webpack，在查找这些没有扩展名的文件时，自动加上.ts或者.js扩展名来匹配。

If Webpack should resolve extension-less files for styles and HTML, add .css and .html to the list.

如果我们希望Webapck也能解析不带扩展名的样式和HTML文件，在列表里追加.css和.html即可。

{@a common-rules}

module.rules

Rules tell Webpack which loaders to use for each file, or module:

Rules用来告诉Webpack加载不同文件或模块时该用哪个加载器。

• awesome-typescript-loader—a loader to transpile the Typescript code to ES5, guided by the tsconfig.json file.

  awesome-typescript-loader - 一个用于把TypeScript代码转译成ES5的加载器，它会由tsconfig.json文件提供指导

• angular2-template-loader—loads angular components' template and styles.

  angular2-template-loader - 用于加载Angular组件的模板和样式

• html-loader—for component templates.

  html-loader - 为组件模板准备的加载器

• images/fonts—Images and fonts are bundled as well.

  images/fonts - 图片和字体文件也能被打包。

• CSS—the first pattern matches application-wide styles; the second handles component-scoped styles (the ones specified in a component's styleUrls metadata property).

  CSS - 第一个模式匹配应用级样式，第二个模式匹配组件局部样式(就是在组件元数据的styleUrls属性中指定的那些)。

The first pattern is for the application-wide styles. It excludes .css files within the src/app directory where the component-scoped styles sit. The ExtractTextPlugin (described below) applies the style and css loaders to these files.

第一个模式是给全局样式使用的，它排除了/src/app目录下的.css文件，因为那里放着我们的组件局部样式。 它只包含了那些位于/src/app及其上级目录的.css文件，那里是应用级样式。 ExtractTextPlugin(后面会讲到)使用style和css加载器来处理这些文件。

The second pattern filters for component-scoped styles and loads them as strings via the raw-loader, which is what Angular expects to do with styles specified in a styleUrls metadata property.

第二个模式过滤器是给组件局部样式的，并通过raw加载器把它们加载成字符串 —— 那是Angular期望通过元数据的styleUrls属性来指定样式的形式。

Multiple loaders can be chained using the array notation.

多重加载器也能使用数组形式串联起来。

{@a common-plugins}

plugins

Finally, create instances of three plugins:

最后，创建三个插件实例：

{@a commons-chunk-plugin}

CommonsChunkPlugin

The app.js bundle should contain only application code. All vendor code belongs in the vendor.js bundle.

app.js包应该只包含应用代码。所有第三方代码都应该放进vendor.js包中。

Of course the application code imports vendor code. On its own,Webpack is not smart enough to keep the vendor code out of the app.js bundle. The CommonsChunkPlugin does that job.

当然，应用代码中还是要imports第三方代码。 Webpack还没有智能到自动把提供商代码排除在app.js包之外的程度。 CommonsChunkPlugin插件能完成此工作。

The CommonsChunkPlugin identifies the hierarchy among three chunks: app -> vendor -> polyfills. Where Webpack finds that app has shared dependencies with vendor, it removes them from app. It would remove polyfills from vendor if they shared dependencies, which they don't.

CommonsChunkPlugin标记出了三个_块_之间的等级体系：app -> vendor -> polyfills。 当Webpack发现app与vendor有共享依赖时，就把它们从app中移除。 在vendor和polyfills之间有共享依赖时也同样如此(虽然它们没啥可共享的)。

{@a html-webpack-plugin}

HtmlWebpackPlugin

Webpack generates a number of js and CSS files. You could insert them into the index.html manually. That would be tedious and error-prone. Webpack can inject those scripts and links for you with the HtmlWebpackPlugin.

Webpack生成了一些js和css文件。 虽然我们_可以手动_把它们插入到index.html中，但那样既枯燥又容易出错。 Webpack可以通过HtmlWebpackPlugin自动为我们注入那些script和link标签。

{@a environment-configuration}

Environment-specific configuration

环境相关的配置

The webpack.common.js configuration file does most of the heavy lifting. Create separate, environment-specific configuration files that build on webpack.common by merging into it the peculiarities particular to the target environments.

webpack.common.js配置做了大部分繁重的工作。 通过合并它们特有的配置，我们可以基于webpack.common为目标环境创建独立的、环境相关的配置文件。

These files tend to be short and simple.

这些文件越小越简单越好。

{@a development-configuration}

Development configuration

开发环境配置

Here is the webpack.dev.js development configuration file.

下面是开发环境的而配置文件webpack.dev.js：

The development build relies on the Webpack development server, configured near the bottom of the file.

开发环境下的构建依赖于Webpack的开发服务器，我们在靠近文件底部的地方配置了它。

Although you tell Webpack to put output bundles in the dist folder, the dev server keeps all bundles in memory; it doesn't write them to disk. You won't find any files in the dist folder ,at least not any generated from this development build.

虽然我们告诉Webpack把输出包放到dist目录，但实际上开发服务器把这些包都放在了内存里，而不会把它们写到硬盘中。 所以在dist目录下是找不到任何文件的(至少现在这个开发环境下构建时没有)。

The HtmlWebpackPlugin ,added in webpack.common.js, uses the publicPath and the filename settings to generate appropriate <script> and <link> tags into the index.html.

HtmlWebpackPlugin(由webpack.common.js引入)插件使用了*publicPath和filename*设置， 来向index.html中插入适当的<script>和<link>标签。

The CSS styles are buried inside the Javascript bundles by default. The ExtractTextPlugin extracts them into external .css files that the HtmlWebpackPlugin inscribes as <link> tags into the index.html.

默认情况下，我们这些CSS样式会被埋没在JavaScript包中。ExtractTextPlugin会把它们提取成外部.css文件， 这样HtmlWebpackPlugin插件就会转而把一个<link>标签写进index.html了。Refer to the Webpack documentation for details on these and other configuration options in this file.要了解本文件中这些以及其它配置项的详情，请参阅Webpack文档。

Grab the app code at the end of this guide and try:

抓取本指南底部的应用代码，并试一试：

npm start

{@a production-configuration}

Production configuration

产品环境配置

Configuration of a production build resembles development configuration with a few key changes.

产品环境下的配置和开发环境下的配置很相似……除了一些关键的改动。

You'll deploy the application and its dependencies to a real production server. You won't deploy the artifacts needed only in development.

我们希望把应用程序及其依赖都部署到一个真实的产品服务器中。 而不希望部署那些只在开发环境下才用得到的依赖。

Put the production output bundle files in the dist folder.

把产品环境的输出包放在dist目录下。

Webpack generates file names with cache-busting hash. Thanks to the HtmlWebpackPlugin, you don't have to update the index.html file when the hash changes.

Webpack生成的文件名中带有“缓存无效哈希(cache-busting hash)”。 感谢HtmlWebpackPlugin插件，当这些哈希值变化时，我们不用去更新index.html了。

There are additional plugins:

还有一些别的插件：

• *NoEmitOnErrorsPlugin— stops the build if there is an error.

  NoEmitOnErrorsPlugin - 如果出错就停止构建。*

*UglifyJsPlugin— minifies the bundles.

UglifyJsPlugin - 最小化(minify)生成的包。

• *ExtractTextPlugin— extracts embedded css as external files, adding cache-busting hash to the filename.

  ExtractTextPlugin - 把内嵌的css抽取成外部文件，并为其文件名添加“缓存无效哈希”。

• *DefinePlugin— use to define environment variables that you can reference within the application.

  DefinePlugin - 用来定义环境变量，以便我们在自己的程序中引用它。

• *LoaderOptionsPlugins— to override options of certain loaders.

  LoaderOptionsPlugins - 为特定的加载器提供选项。

Thanks to the DefinePlugin and the ENV variable defined at top, you can enable Angular production mode like this:

感谢DefinePlugin和顶部定义的ENV变量，我们就可以像这样启用Angular的产品模式了：

Grab the app code at the end of this guide and try:

抓取本指南底部的应用代码，并试一试：

npm run build

{@a test-configuration}

Test configuration

测试环境配置

You don't need much configuration to run unit tests. You don't need the loaders and plugins that you declared for your development and production builds. You probably don't need to load and process the application-wide styles files for unit tests and doing so would slow you down; you'll use the null loader for those CSS files.

我们并不需要使用很多配置项来运行单元测试。 也不需要在开发环境和产品环境下引入的那些加载器和插件。 如果有可能拖慢执行速度，甚至都不需要在单元测试中加载和处理应用全局样式文件，所以我们用一个null加载器来处理所有CSS。

You could merge the test configuration into the webpack.common configuration and override the parts you don't want or need. But it might be simpler to start over with a completely fresh configuration.

我们可以把测试环境的配置合并到webpack.common配置中，并且改写不想要或不需要的部分。 但是从一个全新的配置开始可能更简单。

Reconfigure Karma to use Webpack to run the tests:

重新配置Karma，让它使用webpack来运行这些测试：

You don't precompile the TypeScript; Webpack transpiles the Typescript files on the fly, in memory, and feeds the emitted JS directly to Karma. There are no temporary files on disk.

我们不用预编译TypeScript，Webpack随时在内存中转译我们的TypeScript文件，并且把产出的JS直接反馈给Karma。 硬盘上没有任何临时文件。

The karma-test-shim tells Karma what files to pre-load and primes the Angular test framework with test versions of the providers that every app expects to be pre-loaded.

karma-test-shim告诉Karma哪些文件需要预加载，首要的是：带有“测试版提供商”的Angular测试框架是每个应用都希望预加载的。

Notice that you do not load the application code explicitly. You tell Webpack to find and load the test files (the files ending in .spec.ts). Each spec file imports all—and only—the application source code that it tests. Webpack loads just those specific application files and ignores the other files that you aren't testing.

注意，我们_并没有_明确加载这些应用代码。 只是告诉Webpack查找并加载我们的测试文件(文件名以.spec.ts结尾)。 每个规约(spec)文件都导入了所有(也只有)它测试所需的应用源码。 Webpack只加载_那些_特定的应用文件，而忽略所有其它我们不会测试到的。

Grab the app code at the end of this guide and try:

抓取本指南底部的应用代码，并试一试：

npm test

{@a try}

Trying it out

试一试

Here is the source code for a small application that bundles with the Webpack techniques covered in this guide.

这里是一个小型应用的全部源码，我们可以用本章中学到的Webpack技术打包它们。

The app.component.html displays this downloadable Angular logo . Create a folder called images under the project's assets folder, then right-click (Cmd+click on Mac) on the image and download it to that folder.

app.component.html显示了这个可下载的Angular Logo 。 在项目的assets目录下创建一个名叫images的文件夹，然后右键点击（Mac上是Cmd+点击）本图片，并把它下载到images文件夹中。

{@a bundle-ts}

Here again are the TypeScript entry-point files that define the polyfills and vendor bundles.

这里又是TypeScript的入口点文件，它定义了polyfills和vendor这两个包。

{@a highlights}

Highlights

重点：

• There are no <script> or <link> tags in the index.html. The HtmlWebpackPlugin inserts them dynamically at runtime.

  在index.html中没有<script>或<link>标签。 HtmlWebpackPlugin会在运行时动态插入它们。

• The AppComponent in app.component.ts imports the application-wide css with a simple import statement.

  app.component.ts中的AppComponent类简单的用一个import语句导入了应用级css。

• The AppComponent itself has its own html template and css file. WebPack loads them with calls to require(). Webpack stashes those component-scoped files in the app.js bundle too. You don't see those calls in the source code; they're added behind the scenes by the angular2-template-loader plug-in.

  AppComponent组件本身有它自己的HTML模板和CSS文件。Webpack通过调用require()方法加载它们。Webpack还把那些组件内部的文件打包进了app.js中。 我们在自己的源码中看不到这些调用，这些工作是由幕后的angular2-template-loader插件完成的。

• The vendor.ts consists of vendor dependency import statements that drive the vendor.js bundle. The application imports these modules too; they'd be duplicated in the app.js bundle if the CommonsChunkPlugin hadn't detected the overlap and removed them from app.js.

  vendor.ts由import提供商依赖的语句组成，它最终决定了vender.js的内容。 本应用也导入这些模块，如果没有CommonsChunkPlugin插件检测出这种重叠，并且把它们从app.js中移除，它们就会同时出现在app.js包中。 {@a conclusion}

Conclusion

总结

You've learned just enough Webpack to configurate development, test and production builds for a small Angular application.

我们学到了刚好够用来在开发、测试、产品环境下构建一个小型Angular应用的Webpack配置知识。

You could always do more. Search the web for expert advice and expand your Webpack knowledge.

但我们还能做得更多。搜索互联网来获得专家的建议，并扩展你对Webpack的认识。

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