Use requestAnimationFrame in a class

Question

I'm having problem finding out how I can use requestAnimationFrame in a class.

This code is working fine:

window.onload = function () {
    var width = 20;
    function animation() {
        width++;
        var element = document.getElementById("box");
        element.style.width = width + "px";
        requestAnimationFrame(animation);
    }
    requestAnimationFrame(animation);
};

But when I try putting it into a class, I don't get any result.

class Animation{
    width: number = 20;

    constructor() {
        requestAnimationFrame(this.loop);
    }
    loop() {
        this.width++;
        var element = document.getElementById("box");
        element.style.width = this.width + "px";
        requestAnimationFrame(this.loop);
    }
}
window.onload = function () {
    var animation = new Animation();
};

Could someone tell me what's wrong here?

Answer 1

requestAnimationFrame(this.loop); If you are passing someone else a function that they are going to call use an arrow i.e requestAnimationFrame(()=>this.loop()); or loop = () => {

More : https://www.youtube.com/watch?v=tvocUcbCupA