frameScheduler.js

function frameScheduler (fps) {
	var highPriWork = [];
	var lowPriWork = [];
	var highPriWorkLen = 0;
	var lowPriWorkLen = 0;
	var frameBudget = 1000 / fps;
	var lastTime = 0;
	var asyncCallback;

	var Promise = window.Promise;
	var requestAnimationFrame = window.requestAnimationFrame;

	var promiseSupport = Promise !== void 0;
	var requestAnimationFrameSupport = requestAnimationFrame !== void 0;

	if (promiseSupport) {
		asyncCallback = function asyncCallback (callback) { Promise.resolve().then(callback); }
	} else if (requestAnimationFrameSupport) {
		asyncCallback = function asyncCallback (callback) { requestAnimationFrame(callback); }
	} else {
		asyncCallback = function asyncCallback (callback) { setTimeout(callback, 0); }
	}

	function flushWork (highPriority) {
		var task = highPriority ? highPriWork.shift() : lowPriWork.shift();

		var func = task[0];
		var length = task[1];
		var args = length !== 0 ? task[2] : null;
		var context = task[3];

		switch (length) {
			case 0: func.call(context); break;
			case 1: func.call(context, args[0]); break;
			case 2: func.call(context, args[0], args[1]); break;
			case 3: func.call(context, args[0], args[1], args[2]); break;
			case 4: func.call(context, args[0], args[1], args[2], args[3]); break;
			case 5: func.call(context, args[0], args[1], args[2], args[3], args[4]); break;
			case 6: func.call(context, args[0], args[1], args[2], args[3], args[4], args[5]); break;
		}
	}

	function throttleWork () {
		var time = Date.now();
		var delta = time - lastTime;

		if (delta > frameBudget) {
			lastTime = time - (delta % frameBudget);
			
			if (highPriWorkLen !== 0) {
				flushWork((highPriWorkLen--, true));
			} else if (lowPriWorkLen !== 0) {
				flushWork((lowPriWorkLen--, false));
			}
		} else if (highPriWorkLen !== 0 || lowPriWorkLen !== 0) {
			asyncCallback(throttleWork);
		}
	}
	
	/**
	 * @param {boolean}  highPriority
	 * @param {function} func
	 * @param {number}   length  - number of arguments passed to func
	 * @param {args}     args    - arguments passed to func
	 * @param {context}  context - the this context to execute the function with
	 */
	return function assignWork (highPriority, func, length, args, context) {
		if (highPriority) {
			highPriWork[highPriWorkLen++] = [func, length, args, context];
		} else {
			lowPriWork[lowPriWorkLen++] = [func, length, args, context];
		}

		asyncCallback(throttleWork);
	}
}

a visualisation of work timeline cycles - https://codepen.io/thysultan/pen/VPboOB.