code: function (cmdName) {
              cmdName = cmdName.toLowerCase();
              var me = this,
                  result,
                  cmd = me.commands[cmdName] || UE.commands[cmdName];
              if (!cmd || !cmd.execCommand) {
                  return null;
              }
              if (!cmd.notNeedUndo && !me.__hasEnterExecCommand) {
                  me.__hasEnterExecCommand = true;
                  if (me.queryCommandState.apply(me,arguments) != -1) {
                      me.fireEvent('saveScene');
                      me.fireEvent.apply(me, ['beforeexeccommand', cmdName].concat(arguments));
                      result = this._callCmdFn('execCommand', arguments);
                      //保存场景时，做了内容对比，再看是否进行contentchange触发，这里多触发了一次，去掉
  //                    (!cmd.ignoreContentChange && !me._ignoreContentChange) && me.fireEvent('contentchange');
                      me.fireEvent.apply(me, ['afterexeccommand', cmdName].concat(arguments));
                      me.fireEvent('saveScene');
                  }
                  me.__hasEnterExecCommand = false;
              } else {
                  result = this._callCmdFn('execCommand', arguments);
                  (!me.__hasEnterExecCommand && !cmd.ignoreContentChange && !me._ignoreContentChange) && me.fireEvent('contentchange')
              }
              (!me.__hasEnterExecCommand && !cmd.ignoreContentChange && !me._ignoreContentChange) && me._selectionChange();
              return result;
          }
docs: 执行编辑命令cmdName，完成富文本编辑效果
  @method execCommand
  @param { String } cmdName 需要执行的命令
  @remind 具体命令的使用请参考<a href="#COMMAND.LIST">命令列表</a>
  @return { * } 返回命令函数运行的返回值
  @example
  ```javascript
  editor.execCommand(cmdName);
  ```