<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> </head> <body> <input type="input" id="nullvalue" name="nullvalue"> <input type="button" value="ddddddddddddd" onclick="isnull()"> </BODY> <script language="javascript"> function isnull(){ var v = document.getElementById("nullvalue").value; if(typeof v ==undefined||v.length==0){ alert("空"); }} </script> </HTML>
<HTML>
<HEAD>
</head>
<body>
<input type="input" id="nullvalue" name="nullvalue">
<input type="button" value="ddddddddddddd" onclick="isnull()">
</BODY>
<script language="javascript">
function isnull(){
var v = document.getElementById("nullvalue").value; if(typeof v ==undefined||v.length==0){
alert("空");
}}
</script>
</HTML>