版权声明：ByRisonBoy https://blog.csdn.net/Rison_Li/article/details/82953377
代码片段：
<html>
<body>
<form name="form1">
<table border="1">
<th colspan="2">
<center>学生信息</center>
</th>
<tr>
<td>姓名：</td><td width="120" height="10"><input type="text" name="n1" title="姓名"/></td>
</tr>
<tr>
<td>学号：</td><td><input type="text" name="n2" title="学号"/></td>
</tr>
<tr>
<td>年龄：</td><td><input type="text" name="n3" title="年龄"/></td>
</tr>
<tr>
<td>tel：</td><td><input type="text" name="n4" title="tel"/></td>
</tr>
<tr align="center">
<td colspan="2"><input name="button" type="button" value="提交" onClick="check();"/></td>
</tr>
</table>
</form>
</body>
<script language="javascript">
function check(){
for(i = 0; i < form1.length; i++){
if(form1.elements[i].value=="")
alert(form1.elements[i].title+"不能为空！");
}
}
</script>
</html>
结果显示
