<!--把如下代码加入<body>区域中-->
<script langauge="javascript">
function check() {
var l = document.theform.words.length
alert("你已经输入了"+document.theform.words.value.length+"个字母")
}
</script>
<form name="theform">
<INPUT TYPE="text" name = "words" value = "这个输入框中的字母个数能被检测出来" size = 40>
<input type="button" value="检测"onClick="check()">
</form>
