Simple es6 throttle with leading and trailing-edge calls

throttle.js

function throttle(fn, threshold=250) {
	let hold = false;
	let trail;
	let timeout = function() {
		if (trail !== undefined) {
			fn.apply(trail[0], trail[1]);
			trail = undefined;
			setTimeout(timeout, threshold)
		} else {
			hold = false;
		}
	};
	return function(...args) {
		if (!hold) {
			fn.apply(this, args);
			hold = true;
			setTimeout(timeout, threshold);
		} else {
			trail = [this, args];
		}
	};
}