Is it possible to use existing JavaScript objects as types in TypeScript?

Question

I have an existing JavaScript object. I would like to use it in TypeScript as a type, but can't see any way to do it. For example, I have an JavaScript object constructor like this:

function Canvas2D(canvas) { var context = canvas.getContext("2d"); this.clear = function() { context.clearRect(canvas.width, canvas.height); } // lots more methods follow... } 

In my TypeScript I want to declare a variable that is an instance of Canvas2D. I could define it as type "any" but that doesn't give me auto-suggest and kind of negates the benefits of using TypeScript.

class MyApp { private canvas2d: any; // I want this instead //private canvas2d: Canvas2D; constructor(aCanvas) { this.canvas2d = new Canvas2D(aCanvas); } } 

Is there a way to do this in TypeScript?

In JavaScript I could do this:

var canvas2D = new Canvas2D(aCanvas); 

And it (Visual Studio) would know what type of object it was dealing with.

Answer 1

Yes it is possible. You can either port your Canvas2D object to a typescript class and reference the file

/// <reference path="Canvas2D.ts" /> 

inside of the MyApp file.

or

You can create a definition file (Canvas2D.d.ts) that defines the Canvas2D class shape and reference that instead.

/// <reference path="Canvas2D.d.ts" /> 

ex:

declare class Canvas2D { constructor(elem: HTMLCanvasElement); clear(); // Lots more methods here... }