threshold.ts

onScroll(): () => void {
        var last, timeout, threshold = 100;

        return () => {
            var now = Date.now();

            if (last && now < last + threshold) {
                window.clearTimeout(timeout);
                timeout = window.setTimeout(function () {
                    last = now;
                    this.scrollFn();
                }, threshold);
            } else {
                last = now;
                this.scrollFn();
            }
        }
    }