debounce.js

1-debounce.js

// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `immediate` is passed, trigger the function on the
// leading edge, instead of the trailing.
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);
	};
};

// Usage
var myEfficientFn = debounce(function() {
	// All the taxing stuff you do
}, 250);
window.addEventListener('resize', myEfficientFn);

2-Description.md

The debounce function can be a game-changer when it comes to event-fueled performance. If you aren't using a debouncing function with a scroll, resize, key* event, you're probably doing it wrong.The debounce function will not allow a callback to be used more than once per given time frame. This is especially important when assigning a callback function to frequently-firing events.

http://davidwalsh.name/essential-javascript-functions