Using third-party libraries in TypeScript with ambient declarations.

gistfile1.ts

/// <reference path="../Scripts/typings/jquery/jquery.d.ts" />
$('a').click(function () {
    alert('clicked');
});

Revision #1, attempting to use jQuery will give you a compiler error that '$' is not defined.

Revision #2, we have used the declare keyword to define an ambient declaration. This tells the compiler that an external library will define the variable '$'. Using the 'any' type for the variable will tell the compiler to ignore the standard static typing rules for future '$' references.

In this last revision, we have included a reference to the jQuery declarations file downloaded from Github/DefinitelyTyped. The full declaration file gives you much better intellisense than just using a simple variable declaration.