Events with correct scope in TypeScript

gistfile1.ts

class Tracker {
    count = 0;
    constructor() {
        window.addEventListener("mousedown", this.mouseDown);
        window.addEventListener("mouseup", this.mouseUp);
    }
    mouseDown = (ev: MouseEvent) => {
        window.addEventListener("mousemove", this.mouseMove);
    }
    mouseUp = (ev: MouseEvent) => {
        window.removeEventListener("mousemove", this.mouseMove);
    }
    mouseMove = (ev: MouseEvent) => {
        this.count++;
        console.log(this.count);
    }
}
new Tracker();