media.match.js

/*! MediaMatch v.2.0.3 - Testing css media queries in Javascript. Authors & copyright (c) 2013: WebLinc, David Knight. */

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

    // Internal globals
    var _doc        = win.document,
        _viewport   = _doc.documentElement,
        _queries    = [],
        _queryID    = 0,
        _type       = '',
        _features   = {},
                    // only screen
                    // only screen and
                    // not screen
                    // not screen and
                    // screen
                    // screen and
        _typeExpr   = /\s*(only|not)?\s*(screen|print|[a-z\-]+)\s*(and)?\s*/i,
                    // (-vendor-min-width: 300px)
                    // (min-width: 300px)
                    // (width: 300px)
                    // (width)
                    // (orientation: portrait|landscape)
        _mediaExpr  = /^\s*\(\s*(-[a-z]+-)?(min-|max-)?([a-z\-]+)\s*(:?\s*([0-9]+(\.[0-9]+)?|portrait|landscape)(px|em|dppx|dpcm|rem|%|in|cm|mm|ex|pt|pc|\/([0-9]+(\.[0-9]+)?))?)?\s*\)\s*$/,
        _timer      = 0,

        // Helper methods

        /*
            _matches
         */
        _matches = function (media) {
            // screen and (min-width: 400px), screen and (max-width: 500px)
            var mql         = (media.indexOf(',') !== -1 && media.split(',')) || [media],
                mqIndex     = mql.length - 1,
                mqLength    = mqIndex,
                mq          = null,

                // not screen, screen
                negateType      = null,
                negateTypeFound = '',
                negateTypeIndex = 0,
                negate          = false,
                type            = '',

                // (min-width: 400px), (min-width)
                exprListStr = '',
                exprList    = null,
                exprIndex   = 0,
                exprLength  = 0,
                expr        = null,

                prefix      = '',
                length      = '',
                unit        = '',
                value       = '',
                feature     = '',

                match       = false;

            if (media === '') {
                return true;
            }

            do {
                mq          = mql[mqLength - mqIndex];
                negate      = false;
                negateType  = mq.match(_typeExpr);

                if (negateType) {
                    negateTypeFound = negateType[0];
                    negateTypeIndex = negateType.index;
                }

                if (!negateType || ((mq.substring(0, negateTypeIndex).indexOf('(') === -1) && (negateTypeIndex || (!negateType[3] && negateTypeFound !== negateType.input)))) {
                    match = false;
                    continue;
                }

                exprListStr = mq;

                negate = negateType[1] === 'not';

                if (!negateTypeIndex) {
                    type        =  negateType[2];
                    exprListStr = mq.substring(negateTypeFound.length);
                }

                // Test media type
                // Test type against this device or if 'all' or empty ''
                match       = type === _type || type === 'all' || type === '';

                exprList    = (exprListStr.indexOf(' and ') !== -1 && exprListStr.split(' and ')) || [exprListStr];
                exprIndex   = exprList.length - 1;
                exprLength  = exprIndex;

                if (match && exprIndex >= 0 && exprListStr !== '') {
                    do {
                        expr = exprList[exprIndex].match(_mediaExpr);

                        if (!expr || !_features[expr[3]]) {
                            match = false;
                            break;
                        }

                        prefix  = expr[2];
                        length  = expr[5];
                        value   = length;
                        unit    = expr[7];
                        feature = _features[expr[3]];

                        // Convert unit types
                        if (unit) {
                            if (unit === 'px') {
                                // If unit is px
                                value = Number(length);
                            } else if (unit === 'em' || unit === 'rem') {
                                // Convert relative length unit to pixels
                                // Assumed base font size is 16px
                                value = 16 * length;
                            } else if (expr[8]) {
                                // Convert aspect ratio to decimal
                                value = (length / expr[8]).toFixed(2);
                            } else if (unit === 'dppx') {
                                // Convert resolution dppx unit to pixels
                                value = length * 96;
                            } else if (unit === 'dpcm') {
                                // Convert resolution dpcm unit to pixels
                                value = length * 0.3937;
                            } else {
                                // default
                                value = Number(length);
                            }
                        }

                        // Test for prefix min or max
                        // Test value against feature
                        if (prefix === 'min-' && value) {
                            match = feature >= value;
                        } else if (prefix === 'max-' && value) {
                            match = feature <= value;
                        } else if (value) {
                            match = feature === value;
                        } else {
                            match = !!feature;
                        }

                        // If 'match' is false, break loop
                        // Continue main loop through query list
                        if (!match) {
                            break;
                        }
                    } while (exprIndex--);
                }

                // If match is true, break loop
                // Once matched, no need to check other queries
                if (match) {
                    break;
                }
            } while (mqIndex--);

            return negate ? !match : match;
        },

        /*
            _setFeature
         */
        _setFeature = function () {
            // Sets properties of '_features' that change on resize and/or orientation.
            var w   = win.innerWidth || _viewport.clientWidth,
                h   = win.innerHeight || _viewport.clientHeight,
                dw  = win.screen.width,
                dh  = win.screen.height,
                c   = win.screen.colorDepth,
                x   = win.devicePixelRatio;

            _features.width                     = w;
            _features.height                    = h;
            _features['aspect-ratio']           = (w / h).toFixed(2);
            _features['device-width']           = dw;
            _features['device-height']          = dh;
            _features['device-aspect-ratio']    = (dw / dh).toFixed(2);
            _features.color                     = c;
            _features['color-index']            = Math.pow(2, c);
            _features.orientation               = (h >= w ? 'portrait' : 'landscape');
            _features.resolution                = (x && x * 96) || win.screen.deviceXDPI || 96;
            _features['device-pixel-ratio']     = x || 1;
        },

        /*
            _watch
         */
        _watch = function () {
            clearTimeout(_timer);

            _timer = setTimeout(function () {
                var query   = null,
                    qIndex  = _queryID - 1,
                    qLength = qIndex,
                    match   = false;

                if (qIndex >= 0) {
                    _setFeature();

                    do {
                        query = _queries[qLength - qIndex];

                        if (query) {
                            match = _matches(query.mql.media);

                            if ((match && !query.mql.matches) || (!match && query.mql.matches)) {
                                query.mql.matches = match;

                                if (query.listeners) {
                                    for (var i = 0, il = query.listeners.length; i < il; i++) {
                                        if (query.listeners[i]) {
                                            query.listeners[i].call(win, query.mql);
                                        }
                                    }
                                }
                            }
                        }
                    } while(qIndex--);
                }


            }, 10);
        },

        /*
            _init
         */
        _init = function () {
            var head        = _doc.getElementsByTagName('head')[0],
                style       = _doc.createElement('style'),
                info        = null,
                typeList    = ['screen', 'print', 'speech', 'projection', 'handheld', 'tv', 'braille', 'embossed', 'tty'],
                typeIndex   = 0,
                typeLength  = typeList.length,
                cssText     = '#mediamatchjs { position: relative; z-index: 0; }',
                eventPrefix = '',
                addEvent    = win.addEventListener || (eventPrefix = 'on') && win.attachEvent;

            style.type  = 'text/css';
            style.id    = 'mediamatchjs';

            head.appendChild(style);

            // Must be placed after style is inserted into the DOM for IE
            info = (win.getComputedStyle && win.getComputedStyle(style)) || style.currentStyle;

            // Create media blocks to test for media type
            for ( ; typeIndex < typeLength; typeIndex++) {
                cssText += '@media ' + typeList[typeIndex] + ' { #mediamatchjs { position: relative; z-index: ' + typeIndex + ' } }';
            }

            // Add rules to style element
            if (style.styleSheet) {
                style.styleSheet.cssText = cssText;
            } else {
                style.textContent = cssText;
            }

            // Get media type
            _type = typeList[(info.zIndex * 1) || 0];

            head.removeChild(style);

            _setFeature();

            // Set up listeners
            addEvent(eventPrefix + 'resize', _watch, false);
            addEvent(eventPrefix + 'orientationchange', _watch, false);
        };

    _init();

    /*
        A list of parsed media queries, ex. screen and (max-width: 400px), screen and (max-width: 800px)
    */
    return function (media) {
        var id  = _queryID,
            mql = {
                matches         : false,
                media           : media,
                addListener     : function addListener(listener) {
                    _queries[id].listeners || (_queries[id].listeners = []);
                    listener && _queries[id].listeners.push(listener);
                },
                removeListener  : function removeListener(listener) {
                    var query   = _queries[id],
                        i       = 0,
                        il      = 0;

                    if (!query) {
                        return;
                    }

                    il = query.listeners.length;

                    for ( ; i < il; i++) {
                        if (query.listeners[i] === listener) {
                            query.listeners.splice(i, 1);
                        }
                    }
                }
            };

        if (media === '') {
            mql.matches = true;
            return mql;
        }

        mql.matches = _matches(media);

        _queryID = _queries.push({
            mql         : mql,
            listeners   : null
        });

        return mql;
    };
}(window));