code: function parseVariableIdentifier() {
          var token, node = new Node();
  
          token = lex();
  
          if (token.type !== Token.Identifier) {
              if (strict && token.type === Token.Keyword && isStrictModeReservedWord(token.value)) {
                  tolerateUnexpectedToken(token, Messages.StrictReservedWord);
              } else {
                  throwUnexpectedToken(token);
              }
          }
  
          return node.finishIdentifier(token.value);
      }
docs: 12.2 Variable Statement