TypeScript 配置link

TypeScript configurationlink

TypeScript 是 Angular 应用开发中使用的主语言。 它是 JavaScript 的“方言”之一，为类型安全和工具化而做了设计期支持。

TypeScript is a primary language for Angular application development. It is a superset of JavaScript with design-time support for type safety and tooling.

浏览器不能直接执行 TypeScript。它得先用 tsc 编译器转译(transpile)成 JavaScript，而且编译器需要进行一些配置。

Browsers can't execute TypeScript directly. Typescript must be "transpiled" into JavaScript using the tsc compiler, which requires some configuration.

本页面会涵盖 TypeScript 配置与环境的某些方面，这些对 Angular 开发者是很重要的。具体来说包括下列文件：

This page covers some aspects of TypeScript configuration and the TypeScript environment that are important to Angular developers, including details about the following files:

• tsconfig.json - TypeScript 编译器配置。

  tsconfig.json—TypeScript compiler configuration.

• typings - TypesScript 类型声明文件。

  typings—TypesScript declaration files.

配置文件link

Configuration fileslink

一个 Angular 工作区中包含多个 TypeScript 配置文件。在根一级，有两个主要的 TypeScript 配置文件：tsconfig.json 文件和 tsconfig.base.json 文件。

A given Angular workspace contains several TypeScript configuration files. At the root tsconfig.json file specifies the base TypeScript and Angular compiler options that all projects in the workspace inherit.

TypeScript 和 Angular 提供了很多选项，可以用来配置类型检查功能和要生成的输出。更多信息，请参阅 TypeScript 文档中的使用 extends 进行配置继承部分。

The TypeScript and Angular have a wide range of options which can be used to configure type-checking features and generated output. For more information, see the Configuration inheritance with extends section of the TypeScript documentation.

Angular 工作区的初始 tsconfig.base.json 通常是这样的。

The initial tsconfig.json for an Angular workspace typically looks like the following example.

      
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      {
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "outDir": "./dist/out-tsc",
    "sourceMap": true,
    "declaration": false,
    "downlevelIteration": true,
    "experimentalDecorators": true,
    "moduleResolution": "node",
    "importHelpers": true,
    "target": "es2015",
    "module": "es2020",
    "lib": [
      "es2018",
      "dom"
    ]
  }
}
    

noImplicitAny 与 suppressImplicitAnyIndexErrorslink

noImplicitAny and suppressImplicitAnyIndexErrorslink

TypeScript 开发者们在 noImplicitAny 标志应该是 true 还是 false 上存在分歧。 这没有标准答案，你以后还可以修改这个标志。 但是你的选择会在大项目中产生显著差异，所以它值得讨论一番。

TypeScript developers disagree about whether the noImplicitAny flag should be true or false. There is no correct answer and you can change the flag later. But your choice now can make a difference in larger projects, so it merits discussion.

当 noImplicitAny 标志是 false(默认值)时， 如果编译器无法根据变量的用途推断出变量的类型，它就会悄悄的把变量类型默认为 any。这就是隐式 any的含义。

When the noImplicitAny flag is false (the default), and if the compiler cannot infer the variable type based on how it's used, the compiler silently defaults the type to any. That's what is meant by implicit any.

当 noImplicitAny 标志是 true 并且 TypeScript 编译器无法推断出类型时，它仍然会生成 JavaScript 文件。 但是它也会报告一个错误。 很多饱经沧桑的程序员更喜欢这种严格的设置，因为类型检查能在编译期间捕获更多意外错误。

When the noImplicitAny flag is true and the TypeScript compiler cannot infer the type, it still generates the JavaScript files, but it also reports an error. Many seasoned developers prefer this stricter setting because type checking catches more unintentional errors at compile time.

即使 noImplicitAny 标志被设置成了 true，你也可以把变量的类型设置为 any。

You can set a variable's type to any even when the noImplicitAny flag is true.

如果把 noImplicitAny 标志设置为了 true，你可能会得到隐式索引错。 大多数程序员可能觉得这种错误是个烦恼而不是助力。 你可以使用另一个标志来禁止它们。

When the noImplicitAny flag is true, you may get implicit index errors as well. Most developers feel that this particular error is more annoying than helpful. You can suppress them with the following additional flag:

      
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      "suppressImplicitAnyIndexErrors": true
    

TypeScript 类型定义(typings)link

TypeScript typingslink

很多 JavaScript 库，比如 jQuery、Jasmine 测试库和 Angular，会通过新的特性和语法来扩展 JavaScript 环境。 而 TypeScript 编译器并不能原生的识别它们。 当编译器不能识别时，它就会抛出一个错误。

Many JavaScript libraries, such as jQuery, the Jasmine testing library, and Angular, extend the JavaScript environment with features and syntax that the TypeScript compiler doesn't recognize natively. When the compiler doesn't recognize something, it throws an error.

可以使用TypeScript 类型定义文件 —— .d.ts 文件 —— 来告诉编译器你要加载的库的类型定义。

Use TypeScript type definition files—d.ts files—to tell the compiler about the libraries you load.

TypeScript 敏感的编辑器借助这些定义文件来显示这些库中各个特性的类型定义。

TypeScript-aware editors leverage these same definition files to display type information about library features.

很多库在自己的 npm 包中都包含了它们的类型定义文件，TypeScript 编译器和编辑器都能找到它们。Angular 库也是这样的。 任何 Angular 应用程序的 node_modules/@angular/core/ 目录下，都包含几个 d.ts 文件，它们描述了 Angular 的各个部分。

Many libraries include definition files in their npm packages where both the TypeScript compiler and editors can find them. Angular is one such library. The node_modules/@angular/core/ folder of any Angular application contains several d.ts files that describe parts of Angular.

lib.d.ts 文件link

lib.d.tslink

TypeScript 带有一个特殊的声明文件，名为 lib.d.ts。该文件包含了 JavaScript 运行库和 DOM 的各种常用 JavaScript 环境声明。

TypeScript includes a special declaration file called lib.d.ts. This file contains the ambient declarations for various common JavaScript constructs present in JavaScript runtimes and the DOM.

基于 --target，TypeScript 添加额外的环境声明，例如如果目标为 es6 时将添加 Promise。

Based on the --target, TypeScript adds additional ambient declarations like Promise if the target is es6.

默认情况下，目标是 es2015。如果你把目标改为 es5，那么由于包含了声明文件列表，你仍然拥有较新的类型声明：

By default, the target is es2015. If you are targeting es5, you still have newer type declarations due to the list of declaration files included:

      
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      "lib": [
  "es2018",
  "dom"
]
    

安装类型定义文件link

Installable typings fileslink

遗憾的是，很多库 —— jQuery、Jasmine 和 Lodash 等库 —— 都没有在它们自己的 npm 包中包含 d.ts 文件。 幸运的是，它们的作者或社区中的贡献者已经为这些库创建了独立的 d.ts 文件，并且把它们发布到了一个众所周知的位置。

Many libraries—jQuery, Jasmine, and Lodash among them—do not include d.ts files in their npm packages. Fortunately, either their authors or community contributors have created separate d.ts files for these libraries and published them in well-known locations.

你还可以通过 npm 来使用@types/* 范围化包来安装这些类型信息， 而 TypeScript 自从 2.0 开始，可以自动识别它们。

You can install these typings via npm using the @types/* scoped package and Typescript, starting at 2.0, automatically recognizes them.

比如，要安装 jasmine 的类型信息，你可以执行 npm install @types/jasmine --save-dev。

For instance, to install typings for jasmine you run npm install @types/jasmine --save-dev.

编译目标（target）link

targetlink

默认情况下，编译目标是 es2015，只有现代浏览器才支持它。 你可以把编译目标配置为 es5 以指定支持老式浏览器。 Angular CLI 还提供了差异化加载功能，以便使用不同的包来分别支持现代浏览器和老式浏览器。

By default, the target is es2015, which is supported only in modern browsers. You can configure the target to es5 to specifically support legacy browsers. Differential loading is also provided by the Angular CLI to support modern, and legacy browsers with separate bundles.