TypeScript | Array.from | error TS2339: Property 'from' does not exist on type 'ArrayConstructor'

Question

I was googling, but cannot find the information what and how should I add to my project to allow me using ES6 methods like Array.from

__ EDIT: removed prototype word

Answer 1

If you are sure the API exists on your engine at runtime, compile with --lib es6 (or --lib dom,es6 if you are using the DOM APIs).

See Compiler Options documentation for more details.

Answer 2

You can easily extend existing types like so:

interface Array {
    from(arrayLike: any, mapFn?, thisArg?): Array<any>;
}

The problem here is that this will add the function to the array instances and not as a static function like you require.
But that can be done like so:

interface ArrayConstructor {
    from(arrayLike: any, mapFn?, thisArg?): Array<any>;
}

Then you should be able to use Array.from.

Try it out on Playground.

---

Edit

If you need to polyfill the implementation (because the environment in which you intend to run doesn't have it), then this is how:

interface ArrayConstructor {
    from(arrayLike: any, mapFn?, thisArg?): Array<any>;
}

Array.from = function(arrayLike: any, mapFn?, thisArg?): Array<any> {
    // place code from MDN here
}

The polyfill code in MDN.

---

2nd edit

Based on a comment, I'm adding a typed version:

interface ArrayConstructor {
    from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): Array<U>;
    from<T>(arrayLike: ArrayLike<T>): Array<T>;
}

It's an exact copy of how it's defined in the lib.es6.d.ts.