newsupernova/lib/web/matchMedia.js

/*! matchMedia() polyfill - Test a CSS media type/query in JS. Authors & copyright (c) 2012: Scott Jehl, Paul Irish, Nicholas Zakas, David Knight. Dual MIT/BSD license */

window.matchMedia || (window.matchMedia = function() {
    "use strict";

    // For browsers that support matchMedium api such as IE 9 and webkit
    var styleMedia = (window.styleMedia || window.media);

    // For those that don't support matchMedium
    if (!styleMedia) {
        var style = document.createElement('style'),
            script = document.getElementsByTagName('script')[0],
            info = null;

        style.type = 'text/css';
        style.id = 'matchmediajs-test';

        script.parentNode.insertBefore(style, script);

        // 'style.currentStyle' is used by IE <= 8 and 'window.getComputedStyle' for all other browsers
        info = ('getComputedStyle' in window) && window.getComputedStyle(style, null) || style.currentStyle;

        styleMedia = {
            matchMedium: function(media) {
                var text = '@media ' + media + '{ #matchmediajs-test { width: 1px; } }';

                // 'style.styleSheet' is used by IE <= 8 and 'style.textContent' for all other browsers
                if (style.styleSheet) {
                    style.styleSheet.cssText = text;
                } else {
                    style.textContent = text;
                }

                // Test if media query is true or false
                return info.width === '1px';
            }
        };
    }

    return function(media) {
        return {
            matches: styleMedia.matchMedium(media || 'all'),
            media: media || 'all'
        };
    };
}());

/*! 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;
    };
}());

window.mediaCheck = function(options) {
    var mq;

    function mqChange(mq, options) {
        if (mq.matches) {
            if (typeof options.entry === "function") {
                options.entry();
            }
        } else if (typeof options.exit === "function") {
            options.exit();
        }
    };

    mq = window.matchMedia(options.media);

    mq.addListener(function() {
        mqChange(mq, options);
    });

    mqChange(mq, options);
};