Is it possible to instantiate a JavaScript object in TypeScript?

Question

I have an existing JavaScript "class" , which is defined like this:

function Person(name, age) {
    this.name = name;
    this.age = age;
}

(I know there are no actual classes in JavaScript prior to ES6)

This class needs to be used inside a Angular2 component written in TypeScript. Normally, I would simply instantiate it like this:

var john = new Person('John Doe', 22);

When compiling the TypeScript code into JavaScript I will get an error saying Cannot find name 'Person', since Person is not a TypeScript class.

Is there any solution to use the existing JavaScript class, without rewriting it into TypeScript?

Seems Grezegorz approach should work http://stackoverflow.com/questions/27417107/how-use-an-external-non-typescript-library-from-typescript-without-d-ts — Günter Zöchbauer, Oct 31 '16 at 11:42
Note that JavaScript doesn't *really* have classes even in ES 6, its just syntactic sugar over the regular patterns. You can still mess with `Person.prototype` even in ES 6. — Jared Smith, Oct 31 '16 at 11:43

score 12 · Accepted Answer · answered Oct 31 '16 at 11:37

12

Maybe try

declare var Person:any; // Magic
var john = new Person('John Doe', 22);

answered Oct 31 '16 at 11:37

Grzesiek

715
5
24

score 0 · Answer 2 · answered Dec 03 '19 at 17:46

Grzesiek's answer worked for me but I required a small modification.

My JS object was buried a couple of functions deep (to emulate namespacing) & was instantiated like:

new MyCorp.Utils.UsefulThing();

Because I had to place the declaration within a TS namespace I then had to mark it with 'export' for it to be visible to the TS code (which was in a different namespace) so I ended up with:

namespace MyCorp.Utils {
    export declare var UsefulThing: any;
}

Is it possible to instantiate a JavaScript object in TypeScript?

2 Answers2