angular-docs-cn/aio/content/guide/npm-packages.md

# Workspace npm dependencies

The Angular Framework, Angular CLI, and components used by Angular applicatins are packaged as [npm packages](https://docs.npmjs.com/getting-started/what-is-npm "What is npm?") and distributed via the [npm registry](https://docs.npmjs.com/).

You can download and install these npm packages by using the [npm CLI client](https://docs.npmjs.com/cli/install), which is installed with and runs as a [Node.js®](https://nodejs.org "Nodejs.org") application. By default, the Angular CLI uses the npm client.

Alternatively, you can use the [yarn client](https://yarnpkg.com/) for downloading and installing npm packages. 


<div class="alert is-helpful">

See [Getting Started](guide/quickstart#prerequisites) for information about the required versions and installation of Node.js and npm.

If you already have projects running on your machine that use other versions of Node.js and npm, consider using [nvm](https://github.com/creationix/nvm) to manage the multiple versions of Node.js and npm. 

</div>


## `package.json`

Both `npm` and `yarn` install the packages that are identified in a [`package.json`](https://docs.npmjs.com/files/package.json) file.

The CLI command `ng new` creates a `package.json` file when it creates the new workspace. 
This `package.json` is used by all projects in the workspace, including the initial app project that is  created by the CLI when it creates the workspace.   

Initially, this `package.json` includes _a starter set of packages_, some of which are required by Angular and others that support common application scenarios.
You add packages to `package.json` as your application evolves. 
You may even remove some. 

The `package.json` is organized into two groups of packages:

* [Dependencies](guide/npm-packages#dependencies) are essential to *running* applications.
* [DevDependencies](guide/npm-packages#dev-dependencies) are only necessary to *develop* applications.

<div class="alert is-helpful">

**Library developers:** By default, the CLI command [`ng generate library`](cli/generate) creates a `package.json` for the new library. That `package.json` is used when publishing the library to npm.
For more information, see the CLI wiki page [Library Support](https://github.com/angular/angular-cli/wiki/stories-create-library). 
</div>


{@a dependencies}
## Dependencies

The packages listed in the `dependencies` section of `package.json` are essential to *running* applications. 

The `dependencies` section of `package.json` contains:

* [**Angular packages**](#angular-packages): Angular core and optional modules; their package names begin `@angular/`.

* [**Support packages**](#support-packages): 3rd party libraries that must be present for Angular apps to run.

* [**Polyfill packages**](#polyfills): Polyfills plug gaps in a browser's JavaScript implementation.

To add a new dependency, use the [`ng add`](cli/add) command.

{@a angular-packages}
### Angular packages

The following Angular packages are included as dependencies in the default `package.json` file for a new Angular workspace.
For a complete list of Angular packages, see the [API reference](http://angular.io/api?type=package). 

Package name                               | Description
----------------------------------------   | --------------------------------------------------
[**@angular/animations**](api/animations) | Angular's animations library makes it easy to define and apply animation effects such as page and list transitions. For more information, see the [Animations guide](guide/animations).
[**@angular/common**](api/common) | The commonly-needed services, pipes, and directives provided by the Angular team. The [`HttpClientModule`](api/common/http/HttpClientModule) is also here, in the [`@angular/common/http`](api/common/http) subfolder. For more information, see the [HttpClient guide](guide/http).
**@angular/compiler** | Angular's template compiler. It understands templates and can convert them to code that makes the application run and render. Typically you don’t interact with the compiler directly; rather, you use it indirectly via `platform-browser-dynamic` when JIT compiling in the browser. For more information, see the [Ahead-of-time Compilation guide](guide/aot-compiler).
[**@angular/core**](api/core) | Critical runtime parts of the framework that are needed by every application. Includes all metadata decorators, `Component`, `Directive`,  dependency injection, and the component lifecycle hooks.
[**@angular/forms**](api/forms) | Support for both [template-driven](guide/forms) and [reactive forms](guide/reactive-forms). For information about choosing the best forms approach for your app, see [Introduction to forms](guide/forms-overview).
[**@angular/http**](api/http) | Angular's legacy HTTP client, which was deprecated in version 5.0 in favor of [@angular/common/http](api/common/http).
[**@angular/<br />platform&#8209;browser**](api/platform-browser) | Everything DOM and browser related, especially the pieces that help render into the DOM. This package also includes the `bootstrapModuleFactory()` method for bootstrapping applications for production builds that pre-compile with [AOT](guide/aot-compiler).
[**@angular/<br />platform&#8209;browser&#8209;dynamic**](api/platform-browser-dynamic) | Includes [providers](api/core/Provider) and methods to compile and run the app on the client using the [JIT compiler](guide/aot-compiler).
[**@angular/router**](api/router) | The router module navigates among your app pages when the browser URL changes. For more information, see [Routing and Navigation](guide/router).


{@a support-packages}
### Support packages

The following support packages are included as dependencies in the default `package.json` file for a new Angular workspace. 


Package name                               | Description
----------------------------------------   | --------------------------------------------------
[**rxjs**](https://github.com/ReactiveX/rxjs) | Many Angular APIs return [_observables_](guide/glossary#observable). RxJS is an implementation of the proposed [Observables specification](https://github.com/zenparsing/es-observable) currently before the [TC39](http://www.ecma-international.org/memento/TC39.htm) committee, which determines standards for the JavaScript language.
[**zone.js**](https://github.com/angular/zone.js) | Angular relies on zone.js to run Angular's change detection processes when native JavaScript operations raise events.  Zone.js is an implementation of a [specification](https://gist.github.com/mhevery/63fdcdf7c65886051d55) currently before the [TC39](http://www.ecma-international.org/memento/TC39.htm) committee that determines standards for the JavaScript language.


{@a polyfills}
### Polyfill packages

Many browsers lack native support for some features in the latest HTML standards,
features that Angular requires.
[_Polyfills_](https://en.wikipedia.org/wiki/Polyfill) can emulate the missing features.
The [Browser Support](guide/browser-support) guide explains which browsers need polyfills and 
how you can add them.

The `package.json` for a new Angular workspace installs the [core-js](https://github.com/zloirock/core-js) package, 
which polyfills missing features for several popular browser.


{@a dev-dependencies}

## DevDependencies

The packages listed in the `devDependencies` section of `package.json` help you develop the application on your local machine. You don't deploy them with the production application.

To add a new `devDependency`, use either one of the following commands:

<code-example language="sh" class="code-shell">
  npm install --dev &lt;package-name&gt;
</code-example>

<code-example language="sh" class="code-shell">
  yarn add --dev &lt;package-name&gt;
</code-example>

The following `devDependencies` are provided in the default `package.json` file for a new Angular workspace. 


Package name                               | Description
----------------------------------------   | -----------------------------------
[**@angular&#8209;devkit/<br />build&#8209;angular**](https://github.com/angular/angular-cli/) | The Angular build tools.
[**@angular/cli**](https://github.com/angular/angular-cli/) | The Angular CLI tools.
**@angular/<br />compiler&#8209;cli** | The Angular compiler, which is invoked by the Angular CLI's `ng build` and `ng serve` commands.
**@angular/<br />language&#8209;service** | The [Angular language service](guide/language-service) analyzes component templates and provides type and error information that TypeScript-aware editors can use to improve the developer's experience. For example, see the [Angular language service extension for VS Code](https://marketplace.visualstudio.com/items?itemName=Angular.ng-template).
**@types/... ** | TypeScript definition files for 3rd party libraries such as Jasmine and Node.js.
[**codelyzer**](https://www.npmjs.com/package/codelyzer) | A linter for Angular apps whose rules conform to the Angular [style guide](guide/styleguide).
**jasmine/... ** | Packages to support the [Jasmine](https://jasmine.github.io/) test library.
**karma/... ** | Packages to support the [karma](https://www.npmjs.com/package/karma) test runner.
[**protractor**](https://www.npmjs.com/package/protractor) | An end-to-end (e2e) framework for Angular apps. Built on top of [WebDriverJS](https://github.com/SeleniumHQ/selenium/wiki/WebDriverJs).
[**ts-node**](https://www.npmjs.com/package/ts-node) | TypeScript execution environment and REPL for Node.js.
[**tslint**](https://www.npmjs.com/package/tslint) | A static analysis tool that checks TypeScript code for readability, maintainability, and functionality errors.
[**typescript**](https://www.npmjs.com/package/typescript) | The TypeScript language server, including the *tsc* TypeScript compiler.


## Related information

 For information about how the Angular CLI handles packages see the following guides: 
 
 * [Building and serving](guide/build) describes how packages come together to create a development build.
 * [Deployment](guide/deployment) describes how packages come together to create a production build.