在线编辑器怎么写啊!


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>无标题页</title>
    
</head>
<body><!--作为编辑区的iframe-->
<iframe style="width: 100%; height:100" marginwidth="0" marginheight="0" frameborder="1" id="MsgFrame"  src="about:blank"></iframe>
<br /><input type="button" onclick="t('UnderLine')" value="下划线" />
<input type="button" onclick="t('bold')" value="粗体" id="Button1" /> 
<input type="button" onclick="t('JustifyLeft')" value="左对齐" /> 
<input type="button" onclick="t('JustifyCenter')" value="居中对齐" /> <input type="button" onclick="t('JustifyRight')" value="右对齐" /> <input type="button" onclick="t2()" value="增高" /> 
<input type="button" onclick="t3()" value="减少" /> 
<input type="button" onclick="ViewSource()" value="查看源代码" /> <script type="text/javascript" language="javascript">     //使iframe进入编辑状态。
    var editor;
    editor = document.getElementById("MsgFrame").contentWindow; 
     //window.frames["MsgFrame"].document.designMode="On"
     editor.document.open();
     editor.document.writeln('<html><head>');
     editor.document.writeln("</head><body></body></html>");
     editor.document.onclick = "alert()";
     editor.document.close();
     editor.document.designMode = 'On';
     editor.document.contentEditable = true;
     editor.document.charset="gb2312";
    
    function t(s)
    {
        editor.document.execCommand(s,false,null);
    }    //增高
    function t2(){
          var obj=window.frames["MsgFrame"].frameElement;
          
          var height = parseInt(obj.offsetHeight);//获取iframe的高度
          
          if (height+100 >= 100){
            obj.height = height+100;
          }
    }
    //减低
    function t3(){
          var obj=window.frames["MsgFrame"].frameElement;
          
          var height = parseInt(obj.offsetHeight);
          
          if (height-100 >= 100){
            obj.height = height-100;
          }
    }
    function ViewSource(){
        document.getElementById("textarea1").value = document.getElementById("MsgFrame").contentWindow.document.lastChild.outerHTML;
        }
    
</script> 
<br/>
<textarea name="textarea1" rows="20" cols="100"></textarea></body>
</html>hb