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 stackoverflow.com/questions/27417107/… — Günter Zöchbauer
– Günter Zöchbauer, Commented Oct 31, 2016 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
– Jared Smith, Commented Oct 31, 2016 at 11:43

Grzesiek · Accepted Answer · 2016-10-31 11:37:00Z

12

Maybe try

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

answered Oct 31, 2016 at 11:37

Grzesiek

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Jon · Accepted Answer · 2019-12-03 17:46:34Z

0

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;
}

answered Dec 3, 2019 at 17:46

Jon

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