请大家帮忙看一下,这段JS出了什么问题,琢磨好几天了，我就是看着没毛病，但就是实现不了功能！！！！急求ＪＳ高手解决一下吧！！！！！！！！

Question

<select name="zt" id="zt" onchange ="javascript:zt()"> 
  <option values="0" >字体</option> 
  <option values="1">黑体 </option> 
  <option values="2">宋体 </option> 
  <option values="3">Arial </option> 
</select> for(var i=0; i<ztt.length; i++)
{
  if(ztt.options[i].selected ==true)
  {
    //处理代码
  }
} 

Answer 1

             <select name="zt" id="zt" onchange ="javascript:zt()"><option  value ="0">字体</option><option value ="1">黑体</option><option value ="2">宋体</option><option value ="3">Arial</option></select>JavaScript:
   
function zt()
      {
       var ztt=document .getElementById ('zt');
       for(var i=0;i<4;i++)
       {
         if(ztt.options [i].selected==true )
         {
           document .selection.createRange().text="<font face=\"黑体\">"+document .selection.createRange().text+"</font>";             
         }
       }
       
      }这么用了还是不行啊！

Answer 2

<select name="zt" id="zt" onchange="zt()">
<option>字体 </option> 
<option>黑体 </option>
<option>宋体 </option> 
<option>Arial </option> 
</select>
<script>
function zt() 
      { 
       var ztt=document.getElementById ('zt'); 
       if(ztt.selectedIndex =='1') 
       { 
       document.selection.createRange().execCommand("fontname","","黑体");
       } 
       if(ztt.selectedIndex =='2') 
       { 
       document.selection.createRange().execCommand("fontname","","宋体");
       } 
       if(ztt.selectedIndex ==3) 
       { 
       document.selection.createRange().execCommand("fontname","","Arial");
       } 
      } 
</script>
http://zhidao.baidu.com/question/37778560

Answer 3

稍微修改一下，以适应firefox:<p>This is just a test.</p>
    <select name="zt" id="zt" onchange="zt()">
        <option>字体 </option>
        <option>黑体 </option>
        <option>宋体 </option>
        <option>Arial </option>
    </select>    <script>
function zt() 
{
if (document.selection)//IE
{
var ztt=document.getElementById ('zt');        
       if(ztt.selectedIndex =='1') 
       { 
       document.selection.createRange().execCommand("fontname","","黑体");
       } 
       if(ztt.selectedIndex =='2') 
       { 
       document.selection.createRange().execCommand("fontname","","宋体");
       } 
       if(ztt.selectedIndex ==3) 
       { 
       document.selection.createRange().execCommand("fontname","","Arial");
      }
    }
     else if (window.getSelection)//FireFox
     {
var ztt=document.getElementById ('zt');        
       if(ztt.selectedIndex =='1') 
       { 
            var n = document.createElement("SPAN");
n.setAttribute("style","font-family:黑体");
window.getSelection().getRangeAt(0).surroundContents(n);       } 
       if(ztt.selectedIndex =='2') 
       { 
            var n = document.createElement("SPAN");
n.setAttribute("style","font-family:宋体");
window.getSelection().getRangeAt(0).surroundContents(n);
       } 
       if(ztt.selectedIndex ==3) 
       { 
            var n = document.createElement("SPAN");
n.setAttribute("style","font-family:Arial");
window.getSelection().getRangeAt(0).surroundContents(n);
       }
      }
} 
    </script>