循环读取文本框数组

<script type="text/javascript">
var checkForm = function(){
var fmElements = document.forms["fm"].elements;
for(var i=0; i<fmElements.length; i++){
if(fmElements[i].value.length < 1){
alert(fmElements[i].name+"不能为空");
fmElements[i].focus();
return;
}
}
}
</script>
<form id="fm">
<input type="text" name="textfield0" size="30" />
<input type="text" name="textfield1" size="30" />
<input type="text" name="textfield2" size="30" />
<input type="text" name="textfield3" size="30" />
<input type="button" value="提交" onclick="checkForm();" />
</form>