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/*! matchMedia() polyfill addListener/removeListener extension. Author & copyright (c) 2012: Scott Jehl. Dual MIT/BSD license */

(function(){

    // Bail out for browsers that have addListener support

    if (window.matchMedia && window.matchMedia('all').addListener) {

        return false;

    }

    var localMatchMedia = window.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

            clearTimeout(timeoutID);

            timeoutID = 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(window, mql);

                        }

                    }

                }

            }, 30);

        };

    window.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;

                window.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;

    };

}());