14.2.6 length属性.html

javascript即用即差核心对象手册

<form>
   <input type="text" name="txt"><br>
   <input type="button" value="this is a button">
</form>
<div id="info"></div>
<script>
   var len=document.forms[0].length;
   var str="表单中一共有"+len+"个控件，分别为：";
   for(var i=0;i<len;i++)
   {
     str+=document.forms[0].elements[i].type +",";
   }
   document.getElementById("info").innerText=str;
</script>