验证表单内容为空

<script language="javascript">function check() {var myform = document.getElementById("myform"); //获得form表单对象for ( var i = 0; i < myform.length; i++) { //循环form表单if (myform.elements[i].value == "") { //判断每一个元素是否为空alert(myform.elements[i].title + "不能为空！");myform.elements[i].focus(); //元素获得焦点return;}}myform.submit();}</script>