在textarea的光标处插入值

   var textArea=Ext.getCmp(textAreaId);var o = Ext.getDom(textAreaId); //The text box to be inserted   o.focus();      var s = document.selection.createRange();//以先保存选区的方式用于在IE中实现插入         var value = flag;         if (document.selection) {//用于IE      s.text = value;       s.moveEnd('character',value.length);                  s.moveStart('character',value.length);        }         else {//用于FF             o.value = o.value.substr(0, o.selectionStart) + value + o.value.substr(o.selectionEnd);         }