code: function Request_isHeaderCacheUnModified() {
  
          var etagMatches = true,
              notModified = true,
              modifiedSince = this.getRequestHeader('if-modified-since'),
              noneMatch = this.getRequestHeader('if-none-match'),
              cc = this.getRequestHeader('cache-control'),
              lastModified = this.getHeader('last-modified'),
              etag = this.getHeader('etag');
  
  
          // unconditional request
          if (!modifiedSince && !noneMatch) {
              return false;
              // check for no-cache cache request directive
          } else if (cc && cc.indexOf('no-cache') !== -1) {
              return false;
          }
  
          // parse if-none-match
          if (noneMatch) {
              noneMatch = noneMatch.split(/ *, */);
          }
          // if-none-match
          if (noneMatch) {
              etagMatches = ~noneMatch.indexOf(etag) || '*' == noneMatch[0];
          }
          // if-modified-since
          if (modifiedSince) {
              modifiedSince = Date.parse(modifiedSince);
              lastModified = Date.parse(lastModified);
              notModified = lastModified <= modifiedSince;
          }
  
          return !!(etagMatches && notModified);
      }
docs: @since 0.0.1
  @author Igor Ivanovic
  @method Request#isHeaderModified
  
  @description
  Check if header is modified
  @return {boolean}