Hijacking the useful debounce function from underscore.js

debounce.js

function debounce( func, wait, immediate ) {
	let timeout;
	let args;
	let context;
	let timestamp;
	let result;
	
	const now = Date.now || () => new Date().getTime();
	
	const later = function () {
		const last = now() - timestamp;
		
		if ( last < wait && last >= 0 ) {
			timeout = setTimeout( later, wait - last );
		} else {
			timeout = null;
			if ( !immediate ) {
				result = func.apply( context, args );
				if ( !timeout ) context = args = null;
			}
		}
	};
	
	return function () {
		context       = this;
		args          = arguments;
		timestamp     = now();
		const callNow = immediate && !timeout;
		if ( !timeout ) timeout = setTimeout( later, wait );
		if ( callNow ) {
			result  = func.apply( context, args );
			context = args = null;
		}
		
		return result;
	};
}