Simple JS library which creates Google Analytics compatible __utm[z|a|b] cookies

utm_support.js

(function(W, D, L) {
    if (!Date.now) {
        Date.now = function now() {
            return new Date().getTime();
        };
    }

    if (!String.prototype.startsWith) {
        Object.defineProperty(String.prototype, 'startsWith', {
            enumerable: false,
            configurable: false,
            writable: false,
            value: function(searchString, position) {
                position = position || 0;
                return this.lastIndexOf(searchString, position) === position;
            }
        });
    }

    if (!Array.isArray) {
        Array.isArray = function(arg) {
            return Object.prototype.toString.call(arg) === '[object Array]';
        };
    }

    /**
     * Matches referrer urls from 5 biggest search engines.
     * @type {RegExp}
     */
    var SEARCH_ENGINE_REGEX = /^https?:\/\/(?:www\.(google)\..+q=([^&]+)|www\.(bing)\.com\/search.+q=([^&]+)|.+(yahoo).com\/search.+(?:\?p|&p)=([^&]+)|(yandex)\.ru\/yandsearch\?.+text=([^&]+)|www\.(baidu)\.com\/s\?.+wd=([^&]+))/;

    var HOSTNAME = L.hostname;
    if(HOSTNAME.startsWith('www.')) {
        HOSTNAME = HOSTNAME.substring(HOSTNAME.indexOf('.') + 1);
    }

    /**
     * Fetch an object containing all url parameters starting with "utm_"
     * @returns {object} parameters
     */
    var getUTMParams = function() {
        var codes = {};
        codes.length = 0;
        if (L.search.length > 1) {
            var i,
                pair,
                pairs = L.search.substr(1).split("&");
            for (i = 0; i < pairs.length; i++) {
                pair = pairs[i].split("=");
                if(pair[0].startsWith('utm_')) {
                    codes[decodeURIComponent(pair[0])] = pair.length > 1 ? decodeURIComponent(pair[1]) : "";
                    codes.length++;
                }
            }
        }
        return codes;
    };

    /**
     * Compile acquisition data.
     *  1) From the a current utmz cookie.
     *  2) Referrers from a search engine.
     *  3) utm url parameters.
     * @returns {{campaign: null, source: string, medium: string, content: null, term: null}}
     */
    var getAcquisitionData = function() {
        var data = {
            'campaign': '(direct)',
            'source': '(direct)',
            'medium': '(none)',
            'content': null,
            'term': null
        }
        var utmz = getCookie('__utmz');
        if (utmz) {
            var parts = utmz.split('.');
            var campaignData = parts[4].split('|');
            for (var i in campaignData) {
                var pair = campaignData[i].split('=');
                switch (pair[0]) {
                    case 'utmcsr':
                        data.source = pair[1];
                        break;
                    case 'utmcmd':
                        data.medium = pair[1];
                        break;
                    case 'utmccn':
                        data.campaign = pair[1];
                        break;
                    case 'utmctr':
                        data.term = pair[1];
                        break;
                    case 'utmcct':
                        data.content = pair[1];
                        break;
                }
            }
        }

        if (D.referrer) {
            var matches = SEARCH_ENGINE_REGEX.exec(D.referrer);
            if (matches !== null && Array.isArray(matches)) {
                data.source = matches[1] || matches[3] || matches[5] || matches[7] || matches[9] || false;
                data.medium = '(organic)';
            }
        }

        var utmParams = getUTMParams();
        if ('utm_source' in utmParams) {
            data.source = utmParams['utm_source'];
        }
        if ('utm_medium' in utmParams) {
            data.medium = utmParams['utm_medium'];
        }
        if ('utm_campaign' in utmParams) {
            data.campaign = utmParams['utm_campaign'];
        }
        if ('utm_term' in utmParams) {
            data.term = utmParams['utm_term'];
        }
        if ('utm_content' in utmParams) {
            data.content = utmParams['utm_content'];
        }
        return data;
    };


    /**
     * Generate a hash from a string
     * @param {string} str Domain name to hash
     * @returns {number}
     */
    var domainHash = function(str) {
        var b = 1,
            c = 0,
            d;
        if (str) {
            for (b = 0, d = str.length - 1; 0 <= d; d--) {
                c = str.charCodeAt(d);
                b = (b << 6 & 268435455) + c + (c << 14);
                c = b & 266338304;
                if (c != 0) {
                    b = b ^ c >> 21;
                }
            }
        }
        return b;
    };

    /**
     * Create a date object the specified number of years/months/days and minutes in the future.
     * @param years
     * @param months
     * @param days
     * @param minutes
     * @returns {Date}
     */
    var getFutureDate = function(years, months, days, minutes) {
        var date = new Date();
        if (years > 0) {
            date.setYear(date.getFullYear() + years);
        }
        if (months > 0) {
            date.setMonth(date.getMonth() + months);
        }
        if (days > 0) {
            date.setDate(date.getDate() + days);
        }
        if (minutes > 0) {
            date.setMinutes(date.getMinutes() + minutes);
        }
        return date;
    }

    /**
     * Get the value of a cookie.
     * @param {string} name
     * @returns {string|null}
     */
    var getCookie = function(name) {
        return decodeURIComponent(D.cookie.replace(new RegExp("(?:(?:^|.*;)\\s*" + name + "\\s*\\=\\s*([^;]*).*$)|^.*$"), "$1")) || null;
    };

    /**
     * Set the value and expiry date of a cookie.
     * @param {string} name
     * @param {string} value
     * @param {Date|undefined}
     */
    var setCookie = function(name, value, expire) {
        D.cookie = name + '=' + encodeURIComponent(value) + (expire ? '; expires=' + expire.toUTCString() : '') + '; domain=.' + HOSTNAME + '; path=/';
    };

    /**
     * Generate the value of the __utmz cookie.
     * @param {number} domainHash
     * @returns {string}
     */
    var buildUtmz = function(domainHash) {
        var campaignData = [];
        var acqData = getAcquisitionData();
        campaignData.push('utmcsr=' + acqData.source);
        campaignData.push('utmccn=' + acqData.campaign);
        campaignData.push('utmcmd=' + acqData.medium);
        if (!!acqData.term) {
            campaignData.push('utmctr=' + acqData.term);
        }
        if (!!acqData.content) {
            campaignData.push('utmcct=' + acqData.content);
        }

        return [
            domainHash,
            Math.floor(Date.now() / 1000),
            1, 1,
            campaignData.join('|')
        ].join('.');
    };

    /**
     * Generate the value of the __utma cookie.
     * @param {number} domainHash
     * @returns {string}
     */
    var buildUtma = function(domainHash) {
        return domainHash + '.0.0.0.0.0';
    };

    /**
     * Generate the value of the __utmb cookie.
     * @param {number} domainHash
     * @param {number} pagesViewed
     * @returns {string}
     */
    var buildUtmb = function(domainHash, pagesViewed) {
        return domainHash + '.' + pagesViewed + '.0.' + Date.now();
    };


    /*
     * UTMC
     */
    var hostnameHash = getCookie('__utmc');
    if (hostnameHash === null) {
        hostnameHash = domainHash(HOSTNAME);
        setCookie('__utmc', hostnameHash);
    }

    /*
     * UTMZ
     */
    var utmz = buildUtmz(hostnameHash);
    var expire = getFutureDate(0, 6, 0, 0);
    setCookie('__utmz', utmz, expire);

    /*
     * UTMA
     */
    var utma = getCookie('__utma');
    if (utma === null) {
        utma = buildUtma(hostnameHash);
    }
    expire = getFutureDate(2, 0, 0, 0);
    setCookie('__utma', utma, expire);

    /*
     * UTMB
     */
    var utmb = getCookie('__utmb');
    var pagesViewed = 0;
    if (utmb !== null) {
        var parts = utmb.split('.');
        pagesViewed = parseInt(parts[1]);
    }
    utmb = buildUtmb(hostnameHash, ++pagesViewed);
    expire = getFutureDate(0, 0, 0, 30);
    setCookie('__utmb', utmb, expire);

})(window, document, window.location);