Typescript Deep Dive by Basarat Ali Syed

TypeScript Deep Dive
might want to leave // TODO: comments as you go along.**
Third Party JavaScript
You can change your JavaScript to TypeScript, but you can't change the whole world to use JavaScript. This is where
TypeScript's ambient definition support comes in. In the beginning we recommend you create a vendor.d.ts (the .d.ts
extension specifies the fact that this is a declaration file) and start adding dirty stuff to it. Alternatively create a file specific
for the library e.g. jquery.d.ts for jquery.
Note : Well maintained and strongly typed definitions for nearly the top 90% JavaScript libraries out there exists in an
OSS Repository called DefinitelyTyped. We recommend looking there before creating your own definitions as we
present here. Nevertheless this quick and dirty way is vital knowledge to decrease your initial friction with
TypeScript**.
Consider the case of jquery , you can create a trivial definition for it quite easily:
declare var $: any;
Sometimes you might want to add an explicit annotation on something (e.g. JQuery ) and you need something in type
declaration space. You can do that quite easily using the type keyword:
declare type JQuery = any;
declare var $: JQuery;
This provides you an easier future update path.
Again, a high quality jquery.d.ts exists at DefinitelyTyped. But you now know how to overcome any JavaScript ->
TypeScript friction quickly when using third party JavaScript. We will look at ambient declarations in detail next.
JS Migration Guide
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