Throttle function

throttle.js

const Throttle = (delay = 30) => {
    let timer = null;
    let start = null;

    return (cb) => {
        if (start) {
            const remaining = delay - (Date.now() - start);

            clearTimeout(timer);
            timer = setTimeout(() => {
                cb();

                timer = null;
                start = Date.now();
            }, remaining);
        } else {
            cb();

            timer = setTimeout(() => {
                timer = null;
                start = null;
            }, delay);
            start = Date.now();
        }
    };
};

const throttle = new Throttle(1500);

window.onkeydown = (event) => throttle(() => console.log(event.keyCode));