function parse(ua) {

    /** The environment context object. */
    var context = root;

    /** Used to flag when a custom context is provided. */
    var isCustomContext = ua && typeof ua == 'object' && getClassOf(ua) != 'String';

    // Juggle arguments.
    if (isCustomContext) {
      context = ua;
      ua = null;
    }

    /** Browser navigator object. */
    var nav = context.navigator || {};

    /** Browser user agent string. */
    var userAgent = nav.userAgent || '';

    ua || (ua = userAgent);

    /** Used to flag when `thisBinding` is the [ModuleScope]. */
    var isModuleScope = isCustomContext || thisBinding == oldRoot;

    /** Used to detect if browser is like Chrome. */
    var likeChrome = isCustomContext
      ? !!nav.likeChrome
      : /\bChrome\b/.test(ua) && !/internal|\n/i.test(toString.toString());

    /** Internal `[[Class]]` value shortcuts. */
    var objectClass = 'Object',
        airRuntimeClass = isCustomContext ? objectClass : 'ScriptBridgingProxyObject',
        enviroClass = isCustomContext ? objectClass : 'Environment',
        javaClass = (isCustomContext && context.java) ? 'JavaPackage' : getClassOf(context.java),
        phantomClass = isCustomContext ? objectClass : 'RuntimeObject';

    /** Detect Java environments. */
    var java = /\bJava/.test(javaClass) && context.java;

    /** Detect Rhino. */
    var rhino = java && getClassOf(context.environment) == enviroClass;

    /** A character to represent alpha. */
    var alpha = java ? 'a' : '\u03b1';

    /** A character to represent beta. */
    var beta = java ? 'b' : '\u03b2';

    /** Browser document object. */
    var doc = context.document || {};

    /**
     * Detect Opera browser (Presto-based).
     * http://www.howtocreate.co.uk/operaStuff/operaObject.html
     * http://dev.opera.com/articles/view/opera-mini-web-content-authoring-guidelines/#operamini
     */
    var opera = context.operamini || context.opera;

    /** Opera `[[Class]]`. */
    var operaClass = reOpera.test(operaClass = (isCustomContext && opera) ? opera['[[Class]]'] : getClassOf(opera))
      ? operaClass
      : (opera = null);

    /*------------------------------------------------------------------------*/

    /** Temporary variable used over the script's lifetime. */
    var data;

    /** The CPU architecture. */
    var arch = ua;

    /** Platform description array. */
    var description = [];

    /** Platform alpha/beta indicator. */
    var prerelease = null;

    /** A flag to indicate that environment features should be used to resolve the platform. */
    var useFeatures = ua == userAgent;

    /** The browser/environment version. */
    var version = useFeatures && opera && typeof opera.version == 'function' && opera.version();

    /** A flag to indicate if the OS ends with "/ Version" */
    var isSpecialCasedOS;

    /* Detectable layout engines (order is important). */
    var layout = getLayout([
      { 'label': 'EdgeHTML', 'pattern': 'Edge' },
      'Trident',
      { 'label': 'WebKit', 'pattern': 'AppleWebKit' },
      'iCab',
      'Presto',
      'NetFront',
      'Tasman',
      'KHTML',
      'Gecko'
    ]);

    /* Detectable browser names (order is important). */
    var name = getName([
      'Adobe AIR',
      'Arora',
      'Avant Browser',
      'Breach',
      'Camino',
      'Electron',
      'Epiphany',
      'Fennec',
      'Flock',
      'Galeon',
      'GreenBrowser',
      'iCab',
      'Iceweasel',
      'K-Meleon',
      'Konqueror',
      'Lunascape',
      'Maxthon',
      { 'label': 'Microsoft Edge', 'pattern': '(?:Edge|Edg|EdgA|EdgiOS)' },
      'Midori',
      'Nook Browser',
      'PaleMoon',
      'PhantomJS',
      'Raven',
      'Rekonq',
      'RockMelt',
      { 'label': 'Samsung Internet', 'pattern': 'SamsungBrowser' },
      'SeaMonkey',
      { 'label': 'Silk', 'pattern': '(?:Cloud9|Silk-Accelerated)' },
      'Sleipnir',
      'SlimBrowser',
      { 'label': 'SRWare Iron', 'pattern': 'Iron' },
      'Sunrise',
      'Swiftfox',
      'Vivaldi',
      'Waterfox',
      'WebPositive',
      { 'label': 'Yandex Browser', 'pattern': 'YaBrowser' },
      { 'label': 'UC Browser', 'pattern': 'UCBrowser' },
      'Opera Mini',
      { 'label': 'Opera Mini', 'pattern': 'OPiOS' },
      'Opera',
      { 'label': 'Opera', 'pattern': 'OPR' },
      'Chromium',
      'Chrome',
      { 'label': 'Chrome', 'pattern': '(?:HeadlessChrome)' },
      { 'label': 'Chrome Mobile', 'pattern': '(?:CriOS|CrMo)' },
      { 'label': 'Firefox', 'pattern': '(?:Firefox|Minefield)' },
      { 'label': 'Firefox for iOS', 'pattern': 'FxiOS' },
      { 'label': 'IE', 'pattern': 'IEMobile' },
      { 'label': 'IE', 'pattern': 'MSIE' },
      'Safari'
    ]);

    /* Detectable products (order is important). */
    var product = getProduct([
      { 'label': 'BlackBerry', 'pattern': 'BB10' },
      'BlackBerry',
      { 'label': 'Galaxy S', 'pattern': 'GT-I9000' },
      { 'label': 'Galaxy S2', 'pattern': 'GT-I9100' },
      { 'label': 'Galaxy S3', 'pattern': 'GT-I9300' },
      { 'label': 'Galaxy S4', 'pattern': 'GT-I9500' },
      { 'label': 'Galaxy S5', 'pattern': 'SM-G900' },
      { 'label': 'Galaxy S6', 'pattern': 'SM-G920' },
      { 'label': 'Galaxy S6 Edge', 'pattern': 'SM-G925' },
      { 'label': 'Galaxy S7', 'pattern': 'SM-G930' },
      { 'label': 'Galaxy S7 Edge', 'pattern': 'SM-G935' },
      'Google TV',
      'Lumia',
      'iPad',
      'iPod',
      'iPhone',
      'Kindle',
      { 'label': 'Kindle Fire', 'pattern': '(?:Cloud9|Silk-Accelerated)' },
      'Nexus',
      'Nook',
      'PlayBook',
      'PlayStation Vita',
      'PlayStation',
      'TouchPad',
      'Transformer',
      { 'label': 'Wii U', 'pattern': 'WiiU' },
      'Wii',
      'Xbox One',
      { 'label': 'Xbox 360', 'pattern': 'Xbox' },
      'Xoom'
    ]);

    /* Detectable manufacturers. */
    var manufacturer = getManufacturer({
      'Apple': { 'iPad': 1, 'iPhone': 1, 'iPod': 1 },
      'Alcatel': {},
      'Archos': {},
      'Amazon': { 'Kindle': 1, 'Kindle Fire': 1 },
      'Asus': { 'Transformer': 1 },
      'Barnes & Noble': { 'Nook': 1 },
      'BlackBerry': { 'PlayBook': 1 },
      'Google': { 'Google TV': 1, 'Nexus': 1 },
      'HP': { 'TouchPad': 1 },
      'HTC': {},
      'Huawei': {},
      'Lenovo': {},
      'LG': {},
      'Microsoft': { 'Xbox': 1, 'Xbox One': 1 },
      'Motorola': { 'Xoom': 1 },
      'Nintendo': { 'Wii U': 1,  'Wii': 1 },
      'Nokia': { 'Lumia': 1 },
      'Oppo': {},
      'Samsung': { 'Galaxy S': 1, 'Galaxy S2': 1, 'Galaxy S3': 1, 'Galaxy S4': 1 },
      'Sony': { 'PlayStation': 1, 'PlayStation Vita': 1 },
      'Xiaomi': { 'Mi': 1, 'Redmi': 1 }
    });

    /* Detectable operating systems (order is important). */
    var os = getOS([
      'Windows Phone',
      'KaiOS',
      'Android',
      'CentOS',
      { 'label': 'Chrome OS', 'pattern': 'CrOS' },
      'Debian',
      { 'label': 'DragonFly BSD', 'pattern': 'DragonFly' },
      'Fedora',
      'FreeBSD',
      'Gentoo',
      'Haiku',
      'Kubuntu',
      'Linux Mint',
      'OpenBSD',
      'Red Hat',
      'SuSE',
      'Ubuntu',
      'Xubuntu',
      'Cygwin',
      'Symbian OS',
      'hpwOS',
      'webOS ',
      'webOS',
      'Tablet OS',
      'Tizen',
      'Linux',
      'Mac OS X',
      'Macintosh',
      'Mac',
      'Windows 98;',
      'Windows '
    ]);

    /*------------------------------------------------------------------------*/

    /**
     * Picks the layout engine from an array of guesses.
     *
     * @private
     * @param {Array} guesses An array of guesses.
     * @returns {null|string} The detected layout engine.
     */
    function getLayout(guesses) {
      return reduce(guesses, function(result, guess) {
        return result || RegExp('\\b' + (
          guess.pattern || qualify(guess)
        ) + '\\b', 'i').exec(ua) && (guess.label || guess);
      });
    }

    /**
     * Picks the manufacturer from an array of guesses.
     *
     * @private
     * @param {Array} guesses An object of guesses.
     * @returns {null|string} The detected manufacturer.
     */
    function getManufacturer(guesses) {
      return reduce(guesses, function(result, value, key) {
        // Lookup the manufacturer by product or scan the UA for the manufacturer.
        return result || (
          value[product] ||
          value[/^[a-z]+(?: +[a-z]+\b)*/i.exec(product)] ||
          RegExp('\\b' + qualify(key) + '(?:\\b|\\w*\\d)', 'i').exec(ua)
        ) && key;
      });
    }

    /**
     * Picks the browser name from an array of guesses.
     *
     * @private
     * @param {Array} guesses An array of guesses.
     * @returns {null|string} The detected browser name.
     */
    function getName(guesses) {
      return reduce(guesses, function(result, guess) {
        return result || RegExp('\\b' + (
          guess.pattern || qualify(guess)
        ) + '\\b', 'i').exec(ua) && (guess.label || guess);
      });
    }

    /**
     * Picks the OS name from an array of guesses.
     *
     * @private
     * @param {Array} guesses An array of guesses.
     * @returns {null|string} The detected OS name.
     */
    function getOS(guesses) {
      return reduce(guesses, function(result, guess) {
        var pattern = guess.pattern || qualify(guess);
        if (!result && (result =
              RegExp('\\b' + pattern + '(?:/[\\d.]+|[ \\w.]*)', 'i').exec(ua)
            )) {
          result = cleanupOS(result, pattern, guess.label || guess);
        }
        return result;
      });
    }

    /**
     * Picks the product name from an array of guesses.
     *
     * @private
     * @param {Array} guesses An array of guesses.
     * @returns {null|string} The detected product name.
     */
    function getProduct(guesses) {
      return reduce(guesses, function(result, guess) {
        var pattern = guess.pattern || qualify(guess);
        if (!result && (result =
              RegExp('\\b' + pattern + ' *\\d+[.\\w_]*', 'i').exec(ua) ||
              RegExp('\\b' + pattern + ' *\\w+-[\\w]*', 'i').exec(ua) ||
              RegExp('\\b' + pattern + '(?:; *(?:[a-z]+[_-])?[a-z]+\\d+|[^ ();-]*)', 'i').exec(ua)
            )) {
          // Split by forward slash and append product version if needed.
          if ((result = String((guess.label && !RegExp(pattern, 'i').test(guess.label)) ? guess.label : result).split('/'))[1] && !/[\d.]+/.test(result[0])) {
            result[0] += ' ' + result[1];
          }
          // Correct character case and cleanup string.
          guess = guess.label || guess;
          result = format(result[0]
            .replace(RegExp(pattern, 'i'), guess)
            .replace(RegExp('; *(?:' + guess + '[_-])?', 'i'), ' ')
            .replace(RegExp('(' + guess + ')[-_.]?(\\w)', 'i'), '$1 $2'));
        }
        return result;
      });
    }

    /**
     * Resolves the version using an array of UA patterns.
     *
     * @private
     * @param {Array} patterns An array of UA patterns.
     * @returns {null|string} The detected version.
     */
    function getVersion(patterns) {
      return reduce(patterns, function(result, pattern) {
        return result || (RegExp(pattern +
          '(?:-[\\d.]+/|(?: for [\\w-]+)?[ /-])([\\d.]+[^ ();/_-]*)', 'i').exec(ua) || 0)[1] || null;
      });
    }

    /**
     * Returns `platform.description` when the platform object is coerced to a string.
     *
     * @name toString
     * @memberOf platform
     * @returns {string} Returns `platform.description` if available, else an empty string.
     */
    function toStringPlatform() {
      return this.description || '';
    }

    /*------------------------------------------------------------------------*/

    // Convert layout to an array so we can add extra details.
    layout && (layout = [layout]);

    // Detect Android products.
    // Browsers on Android devices typically provide their product IDS after "Android;"
    // up to "Build" or ") AppleWebKit".
    // Example:
    // "Mozilla/5.0 (Linux; Android 8.1.0; Moto G (5) Plus) AppleWebKit/537.36
    // (KHTML, like Gecko) Chrome/70.0.3538.80 Mobile Safari/537.36"
    if (/\bAndroid\b/.test(os) && !product &&
        (data = /\bAndroid[^;]*;(.*?)(?:Build|\) AppleWebKit)\b/i.exec(ua))) {
      product = trim(data[1])
        // Replace any language codes (eg. "en-US").
        .replace(/^[a-z]{2}-[a-z]{2};\s*/i, '')
        || null;
    }
    // Detect product names that contain their manufacturer's name.
    if (manufacturer && !product) {
      product = getProduct([manufacturer]);
    } else if (manufacturer && product) {
      product = product
        .replace(RegExp('^(' + qualify(manufacturer) + ')[-_.\\s]', 'i'), manufacturer + ' ')
        .replace(RegExp('^(' + qualify(manufacturer) + ')[-_.]?(\\w)', 'i'), manufacturer + ' $2');
    }
    // Clean up Google TV.
    if ((data = /\bGoogle TV\b/.exec(product))) {
      product = data[0];
    }
    // Detect simulators.
    if (/\bSimulator\b/i.test(ua)) {
      product = (product ? product + ' ' : '') + 'Simulator';
    }
    // Detect Opera Mini 8+ running in Turbo/Uncompressed mode on iOS.
    if (name == 'Opera Mini' && /\bOPiOS\b/.test(ua)) {
      description.push('running in Turbo/Uncompressed mode');
    }
    // Detect IE Mobile 11.
    if (name == 'IE' && /\blike iPhone OS\b/.test(ua)) {
      data = parse(ua.replace(/like iPhone OS/, ''));
      manufacturer = data.manufacturer;
      product = data.product;
    }
    // Detect iOS.
    else if (/^iP/.test(product)) {
      name || (name = 'Safari');
      os = 'iOS' + ((data = / OS ([\d_]+)/i.exec(ua))
        ? ' ' + data[1].replace(/_/g, '.')
        : '');
    }
    // Detect Kubuntu.
    else if (name == 'Konqueror' && /^Linux\b/i.test(os)) {
      os = 'Kubuntu';
    }
    // Detect Android browsers.
    else if ((manufacturer && manufacturer != 'Google' &&
        ((/Chrome/.test(name) && !/\bMobile Safari\b/i.test(ua)) || /\bVita\b/.test(product))) ||
        (/\bAndroid\b/.test(os) && /^Chrome/.test(name) && /\bVersion\//i.test(ua))) {
      name = 'Android Browser';
      os = /\bAndroid\b/.test(os) ? os : 'Android';
    }
    // Detect Silk desktop/accelerated modes.
    else if (name == 'Silk') {
      if (!/\bMobi/i.test(ua)) {
        os = 'Android';
        description.unshift('desktop mode');
      }
      if (/Accelerated *= *true/i.test(ua)) {
        description.unshift('accelerated');
      }
    }
    // Detect UC Browser speed mode.
    else if (name == 'UC Browser' && /\bUCWEB\b/.test(ua)) {
      description.push('speed mode');
    }
    // Detect PaleMoon identifying as Firefox.
    else if (name == 'PaleMoon' && (data = /\bFirefox\/([\d.]+)\b/.exec(ua))) {
      description.push('identifying as Firefox ' + data[1]);
    }
    // Detect Firefox OS and products running Firefox.
    else if (name == 'Firefox' && (data = /\b(Mobile|Tablet|TV)\b/i.exec(ua))) {
      os || (os = 'Firefox OS');
      product || (product = data[1]);
    }
    // Detect false positives for Firefox/Safari.
    else if (!name || (data = !/\bMinefield\b/i.test(ua) && /\b(?:Firefox|Safari)\b/.exec(name))) {
      // Escape the `/` for Firefox 1.
      if (name && !product && /[\/,]|^[^(]+?\)/.test(ua.slice(ua.indexOf(data + '/') + 8))) {
        // Clear name of false positives.
        name = null;
      }
      // Reassign a generic name.
      if ((data = product || manufacturer || os) &&
          (product || manufacturer || /\b(?:Android|Symbian OS|Tablet OS|webOS)\b/.test(os))) {
        name = /[a-z]+(?: Hat)?/i.exec(/\bAndroid\b/.test(os) ? os : data) + ' Browser';
      }
    }
    // Add Chrome version to description for Electron.
    else if (name == 'Electron' && (data = (/\bChrome\/([\d.]+)\b/.exec(ua) || 0)[1])) {
      description.push('Chromium ' + data);
    }
    // Detect non-Opera (Presto-based) versions (order is important).
    if (!version) {
      version = getVersion([
        '(?:Cloud9|CriOS|CrMo|Edge|Edg|EdgA|EdgiOS|FxiOS|HeadlessChrome|IEMobile|Iron|Opera ?Mini|OPiOS|OPR|Raven|SamsungBrowser|Silk(?!/[\\d.]+$)|UCBrowser|YaBrowser)',
        'Version',
        qualify(name),
        '(?:Firefox|Minefield|NetFront)'
      ]);
    }
    // Detect stubborn layout engines.
    if ((data =
          layout == 'iCab' && parseFloat(version) > 3 && 'WebKit' ||
          /\bOpera\b/.test(name) && (/\bOPR\b/.test(ua) ? 'Blink' : 'Presto') ||
          /\b(?:Midori|Nook|Safari)\b/i.test(ua) && !/^(?:Trident|EdgeHTML)$/.test(layout) && 'WebKit' ||
          !layout && /\bMSIE\b/i.test(ua) && (os == 'Mac OS' ? 'Tasman' : 'Trident') ||
          layout == 'WebKit' && /\bPlayStation\b(?! Vita\b)/i.test(name) && 'NetFront'
        )) {
      layout = [data];
    }
    // Detect Windows Phone 7 desktop mode.
    if (name == 'IE' && (data = (/; *(?:XBLWP|ZuneWP)(\d+)/i.exec(ua) || 0)[1])) {
      name += ' Mobile';
      os = 'Windows Phone ' + (/\+$/.test(data) ? data : data + '.x');
      description.unshift('desktop mode');
    }
    // Detect Windows Phone 8.x desktop mode.
    else if (/\bWPDesktop\b/i.test(ua)) {
      name = 'IE Mobile';
      os = 'Windows Phone 8.x';
      description.unshift('desktop mode');
      version || (version = (/\brv:([\d.]+)/.exec(ua) || 0)[1]);
    }
    // Detect IE 11 identifying as other browsers.
    else if (name != 'IE' && layout == 'Trident' && (data = /\brv:([\d.]+)/.exec(ua))) {
      if (name) {
        description.push('identifying as ' + name + (version ? ' ' + version : ''));
      }
      name = 'IE';
      version = data[1];
    }
    // Leverage environment features.
    if (useFeatures) {
      // Detect server-side environments.
      // Rhino has a global function while others have a global object.
      if (isHostType(context, 'global')) {
        if (java) {
          data = java.lang.System;
          arch = data.getProperty('os.arch');
          os = os || data.getProperty('os.name') + ' ' + data.getProperty('os.version');
        }
        if (rhino) {
          try {
            version = context.require('ringo/engine').version.join('.');
            name = 'RingoJS';
          } catch(e) {
            if ((data = context.system) && data.global.system == context.system) {
              name = 'Narwhal';
              os || (os = data[0].os || null);
            }
          }
          if (!name) {
            name = 'Rhino';
          }
        }
        else if (
          typeof context.process == 'object' && !context.process.browser &&
          (data = context.process)
        ) {
          if (typeof data.versions == 'object') {
            if (typeof data.versions.electron == 'string') {
              description.push('Node ' + data.versions.node);
              name = 'Electron';
              version = data.versions.electron;
            } else if (typeof data.versions.nw == 'string') {
              description.push('Chromium ' + version, 'Node ' + data.versions.node);
              name = 'NW.js';
              version = data.versions.nw;
            }
          }
          if (!name) {
            name = 'Node.js';
            arch = data.arch;
            os = data.platform;
            version = /[\d.]+/.exec(data.version);
            version = version ? version[0] : null;
          }
        }
      }
      // Detect Adobe AIR.
      else if (getClassOf((data = context.runtime)) == airRuntimeClass) {
        name = 'Adobe AIR';
        os = data.flash.system.Capabilities.os;
      }
      // Detect PhantomJS.
      else if (getClassOf((data = context.phantom)) == phantomClass) {
        name = 'PhantomJS';
        version = (data = data.version || null) && (data.major + '.' + data.minor + '.' + data.patch);
      }
      // Detect IE compatibility modes.
      else if (typeof doc.documentMode == 'number' && (data = /\bTrident\/(\d+)/i.exec(ua))) {
        // We're in compatibility mode when the Trident version + 4 doesn't
        // equal the document mode.
        version = [version, doc.documentMode];
        if ((data = +data[1] + 4) != version[1]) {
          description.push('IE ' + version[1] + ' mode');
          layout && (layout[1] = '');
          version[1] = data;
        }
        version = name == 'IE' ? String(version[1].toFixed(1)) : version[0];
      }
      // Detect IE 11 masking as other browsers.
      else if (typeof doc.documentMode == 'number' && /^(?:Chrome|Firefox)\b/.test(name)) {
        description.push('masking as ' + name + ' ' + version);
        name = 'IE';
        version = '11.0';
        layout = ['Trident'];
        os = 'Windows';
      }
      os = os && format(os);
    }
    // Detect prerelease phases.
    if (version && (data =
          /(?:[ab]|dp|pre|[ab]\d+pre)(?:\d+\+?)?$/i.exec(version) ||
          /(?:alpha|beta)(?: ?\d)?/i.exec(ua + ';' + (useFeatures && nav.appMinorVersion)) ||
          /\bMinefield\b/i.test(ua) && 'a'
        )) {
      prerelease = /b/i.test(data) ? 'beta' : 'alpha';
      version = version.replace(RegExp(data + '\\+?$'), '') +
        (prerelease == 'beta' ? beta : alpha) + (/\d+\+?/.exec(data) || '');
    }
    // Detect Firefox Mobile.
    if (name == 'Fennec' || name == 'Firefox' && /\b(?:Android|Firefox OS|KaiOS)\b/.test(os)) {
      name = 'Firefox Mobile';
    }
    // Obscure Maxthon's unreliable version.
    else if (name == 'Maxthon' && version) {
      version = version.replace(/\.[\d.]+/, '.x');
    }
    // Detect Xbox 360 and Xbox One.
    else if (/\bXbox\b/i.test(product)) {
      if (product == 'Xbox 360') {
        os = null;
      }
      if (product == 'Xbox 360' && /\bIEMobile\b/.test(ua)) {
        description.unshift('mobile mode');
      }
    }
    // Add mobile postfix.
    else if ((/^(?:Chrome|IE|Opera)$/.test(name) || name && !product && !/Browser|Mobi/.test(name)) &&
        (os == 'Windows CE' || /Mobi/i.test(ua))) {
      name += ' Mobile';
    }
    // Detect IE platform preview.
    else if (name == 'IE' && useFeatures) {
      try {
        if (context.external === null) {
          description.unshift('platform preview');
        }
      } catch(e) {
        description.unshift('embedded');
      }
    }
    // Detect BlackBerry OS version.
    // http://docs.blackberry.com/en/developers/deliverables/18169/HTTP_headers_sent_by_BB_Browser_1234911_11.jsp
    else if ((/\bBlackBerry\b/.test(product) || /\bBB10\b/.test(ua)) && (data =
          (RegExp(product.replace(/ +/g, ' *') + '/([.\\d]+)', 'i').exec(ua) || 0)[1] ||
          version
        )) {
      data = [data, /BB10/.test(ua)];
      os = (data[1] ? (product = null, manufacturer = 'BlackBerry') : 'Device Software') + ' ' + data[0];
      version = null;
    }
    // Detect Opera identifying/masking itself as another browser.
    // http://www.opera.com/support/kb/view/843/
    else if (this != forOwn && product != 'Wii' && (
          (useFeatures && opera) ||
          (/Opera/.test(name) && /\b(?:MSIE|Firefox)\b/i.test(ua)) ||
          (name == 'Firefox' && /\bOS X (?:\d+\.){2,}/.test(os)) ||
          (name == 'IE' && (
            (os && !/^Win/.test(os) && version > 5.5) ||
            /\bWindows XP\b/.test(os) && version > 8 ||
            version == 8 && !/\bTrident\b/.test(ua)
          ))
        ) && !reOpera.test((data = parse.call(forOwn, ua.replace(reOpera, '') + ';'))) && data.name) {
      // When "identifying", the UA contains both Opera and the other browser's name.
      data = 'ing as ' + data.name + ((data = data.version) ? ' ' + data : '');
      if (reOpera.test(name)) {
        if (/\bIE\b/.test(data) && os == 'Mac OS') {
          os = null;
        }
        data = 'identify' + data;
      }
      // When "masking", the UA contains only the other browser's name.
      else {
        data = 'mask' + data;
        if (operaClass) {
          name = format(operaClass.replace(/([a-z])([A-Z])/g, '$1 $2'));
        } else {
          name = 'Opera';
        }
        if (/\bIE\b/.test(data)) {
          os = null;
        }
        if (!useFeatures) {
          version = null;
        }
      }
      layout = ['Presto'];
      description.push(data);
    }
    // Detect WebKit Nightly and approximate Chrome/Safari versions.
    if ((data = (/\bAppleWebKit\/([\d.]+\+?)/i.exec(ua) || 0)[1])) {
      // Correct build number for numeric comparison.
      // (e.g. "532.5" becomes "532.05")
      data = [parseFloat(data.replace(/\.(\d)$/, '.0$1')), data];
      // Nightly builds are postfixed with a "+".
      if (name == 'Safari' && data[1].slice(-1) == '+') {
        name = 'WebKit Nightly';
        prerelease = 'alpha';
        version = data[1].slice(0, -1);
      }
      // Clear incorrect browser versions.
      else if (version == data[1] ||
          version == (data[2] = (/\bSafari\/([\d.]+\+?)/i.exec(ua) || 0)[1])) {
        version = null;
      }
      // Use the full Chrome version when available.
      data[1] = (/\b(?:Headless)?Chrome\/([\d.]+)/i.exec(ua) || 0)[1];
      // Detect Blink layout engine.
      if (data[0] == 537.36 && data[2] == 537.36 && parseFloat(data[1]) >= 28 && layout == 'WebKit') {
        layout = ['Blink'];
      }
      // Detect JavaScriptCore.
      // http://stackoverflow.com/questions/6768474/how-can-i-detect-which-javascript-engine-v8-or-jsc-is-used-at-runtime-in-androi
      if (!useFeatures || (!likeChrome && !data[1])) {
        layout && (layout[1] = 'like Safari');
        data = (data = data[0], data < 400 ? 1 : data < 500 ? 2 : data < 526 ? 3 : data < 533 ? 4 : data < 534 ? '4+' : data < 535 ? 5 : data < 537 ? 6 : data < 538 ? 7 : data < 601 ? 8 : data < 602 ? 9 : data < 604 ? 10 : data < 606 ? 11 : data < 608 ? 12 : '12');
      } else {
        layout && (layout[1] = 'like Chrome');
        data = data[1] || (data = data[0], data < 530 ? 1 : data < 532 ? 2 : data < 532.05 ? 3 : data < 533 ? 4 : data < 534.03 ? 5 : data < 534.07 ? 6 : data < 534.10 ? 7 : data < 534.13 ? 8 : data < 534.16 ? 9 : data < 534.24 ? 10 : data < 534.30 ? 11 : data < 535.01 ? 12 : data < 535.02 ? '13+' : data < 535.07 ? 15 : data < 535.11 ? 16 : data < 535.19 ? 17 : data < 536.05 ? 18 : data < 536.10 ? 19 : data < 537.01 ? 20 : data < 537.11 ? '21+' : data < 537.13 ? 23 : data < 537.18 ? 24 : data < 537.24 ? 25 : data < 537.36 ? 26 : layout != 'Blink' ? '27' : '28');
      }
      // Add the postfix of ".x" or "+" for approximate versions.
      layout && (layout[1] += ' ' + (data += typeof data == 'number' ? '.x' : /[.+]/.test(data) ? '' : '+'));
      // Obscure version for some Safari 1-2 releases.
      if (name == 'Safari' && (!version || parseInt(version) > 45)) {
        version = data;
      } else if (name == 'Chrome' && /\bHeadlessChrome/i.test(ua)) {
        description.unshift('headless');
      }
    }
    // Detect Opera desktop modes.
    if (name == 'Opera' &&  (data = /\bzbov|zvav$/.exec(os))) {
      name += ' ';
      description.unshift('desktop mode');
      if (data == 'zvav') {
        name += 'Mini';
        version = null;
      } else {
        name += 'Mobile';
      }
      os = os.replace(RegExp(' *' + data + '$'), '');
    }
    // Detect Chrome desktop mode.
    else if (name == 'Safari' && /\bChrome\b/.exec(layout && layout[1])) {
      description.unshift('desktop mode');
      name = 'Chrome Mobile';
      version = null;

      if (/\bOS X\b/.test(os)) {
        manufacturer = 'Apple';
        os = 'iOS 4.3+';
      } else {
        os = null;
      }
    }
    // Newer versions of SRWare Iron uses the Chrome tag to indicate its version number.
    else if (/\bSRWare Iron\b/.test(name) && !version) {
      version = getVersion('Chrome');
    }
    // Strip incorrect OS versions.
    if (version && version.indexOf((data = /[\d.]+$/.exec(os))) == 0 &&
        ua.indexOf('/' + data + '-') > -1) {
      os = trim(os.replace(data, ''));
    }
    // Ensure OS does not include the browser name.
    if (os && os.indexOf(name) != -1 && !RegExp(name + ' OS').test(os)) {
      os = os.replace(RegExp(' *' + qualify(name) + ' *'), '');
    }
    // Add layout engine.
    if (layout && !/\b(?:Avant|Nook)\b/.test(name) && (
        /Browser|Lunascape|Maxthon/.test(name) ||
        name != 'Safari' && /^iOS/.test(os) && /\bSafari\b/.test(layout[1]) ||
        /^(?:Adobe|Arora|Breach|Midori|Opera|Phantom|Rekonq|Rock|Samsung Internet|Sleipnir|SRWare Iron|Vivaldi|Web)/.test(name) && layout[1])) {
      // Don't add layout details to description if they are falsey.
      (data = layout[layout.length - 1]) && description.push(data);
    }
    // Combine contextual information.
    if (description.length) {
      description = ['(' + description.join('; ') + ')'];
    }
    // Append manufacturer to description.
    if (manufacturer && product && product.indexOf(manufacturer) < 0) {
      description.push('on ' + manufacturer);
    }
    // Append product to description.
    if (product) {
      description.push((/^on /.test(description[description.length - 1]) ? '' : 'on ') + product);
    }
    // Parse the OS into an object.
    if (os) {
      data = / ([\d.+]+)$/.exec(os);
      isSpecialCasedOS = data && os.charAt(os.length - data[0].length - 1) == '/';
      os = {
        'architecture': 32,
        'family': (data && !isSpecialCasedOS) ? os.replace(data[0], '') : os,
        'version': data ? data[1] : null,
        'toString': function() {
          var version = this.version;
          return this.family + ((version && !isSpecialCasedOS) ? ' ' + version : '') + (this.architecture == 64 ? ' 64-bit' : '');
        }
      };
    }
    // Add browser/OS architecture.
    if ((data = /\b(?:AMD|IA|Win|WOW|x86_|x)64\b/i.exec(arch)) && !/\bi686\b/i.test(arch)) {
      if (os) {
        os.architecture = 64;
        os.family = os.family.replace(RegExp(' *' + data), '');
      }
      if (
          name && (/\bWOW64\b/i.test(ua) ||
          (useFeatures && /\w(?:86|32)$/.test(nav.cpuClass || nav.platform) && !/\bWin64; x64\b/i.test(ua)))
      ) {
        description.unshift('32-bit');
      }
    }
    // Chrome 39 and above on OS X is always 64-bit.
    else if (
        os && /^OS X/.test(os.family) &&
        name == 'Chrome' && parseFloat(version) >= 39
    ) {
      os.architecture = 64;
    }

    ua || (ua = null);

    /*------------------------------------------------------------------------*/

    /**
     * The platform object.
     *
     * @name platform
     * @type Object
     */
    var platform = {};

    /**
     * The platform description.
     *
     * @memberOf platform
     * @type string|null
     */
    platform.description = ua;

    /**
     * The name of the browser's layout engine.
     *
     * The list of common layout engines include:
     * "Blink", "EdgeHTML", "Gecko", "Trident" and "WebKit"
     *
     * @memberOf platform
     * @type string|null
     */
    platform.layout = layout && layout[0];

    /**
     * The name of the product's manufacturer.
     *
     * The list of manufacturers include:
     * "Apple", "Archos", "Amazon", "Asus", "Barnes & Noble", "BlackBerry",
     * "Google", "HP", "HTC", "LG", "Microsoft", "Motorola", "Nintendo",
     * "Nokia", "Samsung" and "Sony"
     *
     * @memberOf platform
     * @type string|null
     */
    platform.manufacturer = manufacturer;

    /**
     * The name of the browser/environment.
     *
     * The list of common browser names include:
     * "Chrome", "Electron", "Firefox", "Firefox for iOS", "IE",
     * "Microsoft Edge", "PhantomJS", "Safari", "SeaMonkey", "Silk",
     * "Opera Mini" and "Opera"
     *
     * Mobile versions of some browsers have "Mobile" appended to their name:
     * eg. "Chrome Mobile", "Firefox Mobile", "IE Mobile" and "Opera Mobile"
     *
     * @memberOf platform
     * @type string|null
     */
    platform.name = name;

    /**
     * The alpha/beta release indicator.
     *
     * @memberOf platform
     * @type string|null
     */
    platform.prerelease = prerelease;

    /**
     * The name of the product hosting the browser.
     *
     * The list of common products include:
     *
     * "BlackBerry", "Galaxy S4", "Lumia", "iPad", "iPod", "iPhone", "Kindle",
     * "Kindle Fire", "Nexus", "Nook", "PlayBook", "TouchPad" and "Transformer"
     *
     * @memberOf platform
     * @type string|null
     */
    platform.product = product;

    /**
     * The browser's user agent string.
     *
     * @memberOf platform
     * @type string|null
     */
    platform.ua = ua;

    /**
     * The browser/environment version.
     *
     * @memberOf platform
     * @type string|null
     */
    platform.version = name && version;

    /**
     * The name of the operating system.
     *
     * @memberOf platform
     * @type Object
     */
    platform.os = os || {

      /**
       * The CPU architecture the OS is built for.
       *
       * @memberOf platform.os
       * @type number|null
       */
      'architecture': null,

      /**
       * The family of the OS.
       *
       * Common values include:
       * "Windows", "Windows Server 2008 R2 / 7", "Windows Server 2008 / Vista",
       * "Windows XP", "OS X", "Linux", "Ubuntu", "Debian", "Fedora", "Red Hat",
       * "SuSE", "Android", "iOS" and "Windows Phone"
       *
       * @memberOf platform.os
       * @type string|null
       */
      'family': null,

      /**
       * The version of the OS.
       *
       * @memberOf platform.os
       * @type string|null
       */
      'version': null,

      /**
       * Returns the OS string.
       *
       * @memberOf platform.os
       * @returns {string} The OS string.
       */
      'toString': function() { return 'null'; }
    };

    platform.parse = parse;
    platform.toString = toStringPlatform;

    if (platform.version) {
      description.unshift(version);
    }
    if (platform.name) {
      description.unshift(name);
    }
    if (os && name && !(os == String(os).split(' ')[0] && (os == name.split(' ')[0] || product))) {
      description.push(product ? '(' + os + ')' : 'on ' + os);
    }
    if (description.length) {
      platform.description = description.join(' ');
    }
    return platform;
  }
Used to flag when a custom context is provided.