docs: function(userAgent) {
        if(!userAgent || userAgent === ''){
           return 'desktop';
        }
        var uaHash = getUserAgentHash(userAgent);
        var value = userAgentCache.get(uaHash);
        if (!value) {
           // check for tablet first
           var bTabletFound = false;
           tabletRegex.forEach(function(pattern) {
              if (!bTabletFound && pattern.test(userAgent))
                 bTabletFound = true;
           });
  
           if (bTabletFound) {
              value = 'tablet'
           } else {
              // keep searching for more
              if (/mobi/i.test(userAgent)) {
                 value = 'mobile';
              } else {
                 value = 'desktop';
              }
           }
           //Update cache.
           userAgentCache.set(uaHash, value);
        }
  
        return value;
     }