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49 lines
1.4 KiB
Markdown
49 lines
1.4 KiB
Markdown
---
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date: 2020-10-01
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id: afc1ca85-af24-4ef6-bcd8-91193c4fbd32
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title: lib.d.ts
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---
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# Introduction
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This is where TypeScript "cheats" and ships with a file called
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[lib.d.ts](https://github.com/microsoft/TypeScript/blob/master/lib/lib.d.ts).
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This file contains ambient declarations for a whole bunch of common
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[JavaScript](20200613170905-javascript) constructs present in JavaScript
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runtimes and the DOM.
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- This file is automatically included in the compilation context of a
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TypeScript project.
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- The objective of this file is to make it easy for you to start
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writing type checked JavaScript code.
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# Modifying Native Types
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If you want to be a clever clogs you can add stuff to the interfaces in
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lib.d.ts by creating a global module (ie: `global.d.ts`)
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# Example
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## lib.d.ts magic
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The following code is only possible because of lib.d.ts. If it's used
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with the `nolib` option, TypeScript doesn't know that all JavaScript
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objects have a `toString` function.
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var foo = 123;
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var bar = foo.toString();
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## Example of what's in the lib.d.ts
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``` typescript
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declare var window: Window;
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interface Window extends EventTarget, WindowTimers, WindowSessionStorage, WindowLocalStorage, WindowConsole, GlobalEventHandlers, IDBEnvironment, WindowBase64 {
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animationStartTime: number;
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applicationCache: ApplicationCache;
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clientInformation: Navigator;
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closed: boolean;
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crypto: Crypto;
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// so on and so forth...
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}
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```
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