Throttle Javascript Functions

throttle.js

	/**
	* Debounce a function so that it will only fire once
	*
	* USAGE EXAMPLE:
	* $scope.search = debounce(performSearch, 500); // Bind to ng-keyup
	*
	* http://davidwalsh.name/javascript-debounce-function
	*
	* @param func [Function] - The function to execute
	* @param wait [int] - How many milliseconds to debounce
	* @param immediate [boolean] - If true, fires at the leading edge
	* @return [Function]
	*/
  function debounce (func, wait, immediate) {
		var timeout;
		return function() {
			var context = this, args = arguments;
			var later = function() {
				timeout = null;
				if (!immediate) func.apply(context, args);
			};
			var callNow = immediate && !timeout;
			clearTimeout(timeout);
			timeout = setTimeout(later, wait);
			if (callNow) func.apply(context, args);
		};
	};


	/**
	* Throttle a function so that it will not exceed a specified rate
	*
	* USAGE EXAMPLE:
	* $scope.search = throttle(performSearch, 500); // Bind to ng-keyup
	*
	* http://scn.sap.com/community/labs/blog/2014/04/30/debounce-and-throttle-in-javascript
	*
	* @param func [Function] - The function to execute
	* @param wait [int] - How many milliseconds to debounce
	* @param options [object]
	* @return [Function]
	*/
  function throttle (func, wait, options) {
		var context, args, result;
		var timeout = null;
		var previous = 0;
		options || (options = {});

		var later = function() {
			previous = options.leading === false ? 0 : _.now();
			timeout = null;
			result = func.apply(context, args);
			context = args = null;
		};

		return function() {
			var now = _.now();
			if (!previous && options.leading === false) previous = now;

		var remaining = wait - (now - previous);
			context = this;
			args = arguments;
			if (remaining <= 0) {
				clearTimeout(timeout);
				timeout = null;
				previous = now;
				result = func.apply(context, args);
				context = args = null;
			} else if (!timeout && options.trailing !== false) {
				timeout = setTimeout(later, remaining);
			}
			return result;
		};
	};