Mini Shell

/*! matchMedia() polyfill addListener/removeListener extension. Author & copyright (c) 2012: Scott Jehl. Dual MIT/BSD license */
(function( w ){
	"use strict";
	// Bail out for browsers that have addListener support
	if (w.matchMedia && w.matchMedia('all').addListener) {
		return false;
	}

	var localMatchMedia = w.matchMedia,
		hasMediaQueries = localMatchMedia('only all').matches,
		isListening     = false,
		timeoutID       = 0,    // setTimeout for debouncing 'handleChange'
		queries         = [],   // Contains each 'mql' and associated 'listeners' if 'addListener' is used
		handleChange    = function(evt) {
			// Debounce
			w.clearTimeout(timeoutID);

			timeoutID = w.setTimeout(function() {
				for (var i = 0, il = queries.length; i < il; i++) {
					var mql         = queries[i].mql,
						listeners   = queries[i].listeners || [],
						matches     = localMatchMedia(mql.media).matches;

					// Update mql.matches value and call listeners
					// Fire listeners only if transitioning to or from matched state
					if (matches !== mql.matches) {
						mql.matches = matches;

						for (var j = 0, jl = listeners.length; j < jl; j++) {
							listeners[j].call(w, mql);
						}
					}
				}
			}, 30);
		};

	w.matchMedia = function(media) {
		var mql         = localMatchMedia(media),
			listeners   = [],
			index       = 0;

		mql.addListener = function(listener) {
			// Changes would not occur to css media type so return now (Affects IE <= 8)
			if (!hasMediaQueries) {
				return;
			}

			// Set up 'resize' listener for browsers that support CSS3 media queries (Not for IE <= 8)
			// There should only ever be 1 resize listener running for performance
			if (!isListening) {
				isListening = true;
				w.addEventListener('resize', handleChange, true);
			}

			// Push object only if it has not been pushed already
			if (index === 0) {
				index = queries.push({
					mql         : mql,
					listeners   : listeners
				});
			}

			listeners.push(listener);
		};

		mql.removeListener = function(listener) {
			for (var i = 0, il = listeners.length; i < il; i++){
				if (listeners[i] === listener){
					listeners.splice(i, 1);
				}
			}
		};

		return mql;
	};
}( this ));