code: function (wordArray) {
              // Shortcuts
              var thisWords = this.words;
              var thatWords = wordArray.words;
              var thisSigBytes = this.sigBytes;
              var thatSigBytes = wordArray.sigBytes;
  
              // Clamp excess bits
              this.clamp();
  
              // Concat
              if (thisSigBytes % 4) {
                  // Copy one byte at a time
                  for (var i = 0; i < thatSigBytes; i++) {
                      var thatByte = (thatWords[i >>> 2] >>> (24 - (i % 4) * 8)) & 0xff;
                      thisWords[(thisSigBytes + i) >>> 2] |= thatByte << (24 - ((thisSigBytes + i) % 4) * 8);
                  }
              } else {
                  // Copy one word at a time
                  for (var i = 0; i < thatSigBytes; i += 4) {
                      thisWords[(thisSigBytes + i) >>> 2] = thatWords[i >>> 2];
                  }
              }
              this.sigBytes += thatSigBytes;
  
              // Chainable
              return this;
          }
docs: Concatenates a word array to this word array.
  
  @param {WordArray} wordArray The word array to append.
  
  @return {WordArray} This word array.
  
  @example
  
  wordArray1.concat(wordArray2);