anchor.diff:  
   :marked
     TypeScript is a primary language for Angular application development.
  -  
  +
  +  TypeScript是Angular应用开发中使用的主语言。
  +
     TypeScript is a dialect of JavaScript with design-time support for type-safety and tooling.
  -  
  +
  +  TypeScript是JavaScript的“方言”之一，为类型安全和工具化而做了设计期支持。
  +
     Browsers can't execute TypeScript directly. It has to be "transpiled" into JavaScript with the *tsc* compiler
     and that effort requires some configuration.
  -  
  +
  +  浏览器不能直接执行TypeScript。它得先用*tsc*编译器转译(transpile)成JavaScript，而且这项工作需要进行一定的配置。
  +
     This chapter covers some aspects of TypeScript configuration and the TypeScript environment
     that are important to Angular developers.
  -  
  +
  +  本章会覆盖TypeScript配置与环境的某些方面，这些对Angular开发者是很重要的。
  +
     * [tsconfig.json](#tsconfig) - TypeScript compiler configuration.
  +
  +  * [tsconfig.json](#tsconfig) - TypeScript编译器配置。
  +
     * [typings](#typings) - TypesScript declaration files.
  +
  +  * [typings](#typings) - TypesScript类型声明文件。
   
   a(id="tsconfig")
   .l-main-section
  
positive.code: .l-main-section
  :marked
    ## TypeScript Typings
    Many JavaScript libraries such as jQuery, the Jasmine testing library, and Angular itself,
    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. 
    
    We use [TypeScript type definition files](http://www.typescriptlang.org/Handbook#writing-dts-files)
    &mdash; *d.ts files* &mdash; to tell the compiler about the libraries we load.
    
    TypeScript-aware editors leverage these same definition files to display type information about library features.
    
    Many libraries include their definition files in their npm packages where both the TypeScript compiler and editors
    can find them. Angular is one such library. 
    Peek into the `node_modules/@angular/core/` folder of any Angular application to see several `...d.ts` files that describe parts of Angular.
    
    **We need do nothing to get *typings* files for library packages which include *d.ts* files &mdash; as all Angular packages do.**
    
    ### Installable typings files
    Sadly, many libraries &mdash; jQuery, Jasmine, and Lodash among them &mdash; 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.
    The *typings* tool can find and fetch these files for us.
    
    We installed the [typings](https://github.com/typings/typings/blob/master/README.md) tool 
    with npm (it's listed among the *devDependencies* in the `package.json`) and added an npm script
    to run that tool automatically after *npm* installation completes.
  +makeJson('quickstart/ts/package.1.json', {paths: 'scripts.postinstall'}, 'package.json (postinstall)')(format=".")
  :marked
    This *typings* tool command installs the *d.ts* files that we identify in a `typings.json` file into the **typings** folder.
    We created a `typings.json` file in the [QuickStart](../quickstart.html):
  +makeJson('quickstart/ts/typings.1.json', null, 'typings.json')(format=".")
  :marked
    We identified three *typings* file in the QuickStart, the *d.ts* files for
    
    * [core-js](https://github.com/zloirock/core-js/blob/master/README.md)
    that brings ES2015/ES6 capabilities to our ES5 browsers
    
    * [jasmine](http://jasmine.github.io/) typings for the Jasmine test framework
    
    * [node](https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/node/node.d.ts) for code that references objects in the nodejs environment; 
    see the [webpack](./webpack.html) chapter for an example.
    
    QuickStart itself doesn't require these typings but many of the documentation samples do.
    Most of us would be disappointed if we couldn't code against 
    typical ES2015 features or support testing right out-of-the-box.
  
    We can also run the *typings* tool ourselves.
    The following command (re)installs the typings files, as is sometimes necessary when the `postInstall` hook fails to do so.
  code-example(format="").
    npm run typings install
  :marked
    This command lists the installed typings files:
  code-example(format="").
    npm run typings list
  :marked
    The following command installs or updates the typings file for the Jasmine test library from the *DefinitelyTyped* repository
    and updates the `typings.config` so we that we get it automatically the next time we install typings.
  code-example(format="").
    npm run typings -- install dt~jasmine --save --global
  .l-sub-section
    :marked
      The [&ndash;&ndash; option](https://docs.npmjs.com/cli/run-script) is important; 
      it tells npm to pass all arguments to the right of `--` to the *typings* command.
      
      Learn about the features of the *typings* tool at its [site on github](https://github.com/typings/typings/blob/master/README.md).
  
  
negative.code:   ## *tsconfig.json*
    We typically add a TypeScript configuration file (`tsconfig.json`) to our project to
    guide the compiler as it generates JavaScript files.
  
    我们通常会往项目中加入一个TypeScript配置文件(`tsconfig.json`)，来指导编译器如何生成JavaScript文件。
  .l-sub-section
    :marked
      Get details about `tsconfig.json` from the official
      [TypeScript wiki](https://github.com/Microsoft/TypeScript/wiki/tsconfig.json).
  
      要了解关于`tsconfig.json`的详情，请参阅官方提供的
      [TypeScript wiki](https://github.com/Microsoft/TypeScript/wiki/tsconfig.json)。
  :marked
    We created the following `tsconfig.json` for the [QuickStart](../quickstart.html):
  
    我们在[快速起步](../quickstart.html)中创建过如下的`tsconfig.json`：
  
  +makeJson('quickstart/ts/tsconfig.1.json', null, 'tsconfig.json')(format=".")
  :marked
    The options and flags in this file are essential for Angular 2 applications.
  
    该文件中的选项和标志是写Angular 2应用程序的基础。
  
    <a id="noImplicitAny"></a>
    ### *noImplicitAny* and *suppressImplicitAnyIndexErrors*
    ### *noImplicitAny*与*suppressImplicitAnyIndexErrors*
  
    TypeScript developers disagree about whether the `noImplicitAny` flag should be `true` or `false`.
    There is no correct answer and we can change the flag later.
    But our choice now can make a difference in larger projects so it merits discussion.
  
    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，我们以后还可以修改这个标志。
    但是我们的选择会在大项目中产生显著差异，所以它值得讨论一番。
  
    When the `noImplicitAny` flag is `false` (the default),
    the compiler silently defaults the type of a variable to `any` if it cannot infer
    the type based on how the variable is used. That's what we mean by *implicit `any`*.
  
    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。
  
    We initialized the `noImplicitAny` flag to `false` in the QuickStart
    to make learning TypeScript development easier.
  
    我们在“快速起步”中把`noImplicitAny`标志初始化为`false`，是为了让学习TypeScript开发更简单点儿。
  
    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.
  
    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。
  
    We can set a variable's type to `any` even when the `noImplicitAny` flag is `true`.
    We do so when that seems like the best choice for the situation,
    deliberately and explicitly, after giving the matter some thought.
  
    即使`noImplicitAny`标志设置为`true`，我们也仍然能把变量的类型指定为`any`。
    在经过了审慎而明确的评估之后，如果某种情况下它看起来确实是最佳选择，那我们就这么做。
  
    If we set the `noImplicitAny` flag to `true`, we may get *implicit index errors* as well.
    Most developers feel that *this particular error* is more annoying than helpful.
    We can suppress them with the following additional flag.
  
    如果我们把`noImplicitAny`标志设置为了`true`，我们可能会得到*隐式索引错*。
    大多数程序员可能觉得*这种错误*是个是个烦恼而不是助力。
    我们可以使用下列附加标志来禁止它们。
  code-example(format=".").
    "suppressImplicitAnyIndexErrors":true
  
  