在提交之前
<script>
function checkit()
{
if(document.form1.T1.value==""){alert("名称不能为空,请重新输入");document.form1.T1.focus();return false;}
if(...){...}return ture;
}
</script>
<form name="form1" onSubmit="javascript:return checkit()">
</form>
<script>
function checkit()
{
if(document.form1.T1.value==""){alert("名称不能为空,请重新输入");document.form1.T1.focus();return false;}
if(...){...}return ture;
}
</script>
<form name="form1" onSubmit="javascript:return checkit()">
</form>
<script>
function trim(obj){
return obj.replace(/(^\s*)|(\s*$)/g, "");
}
function adjust(){
var a = document.form1.t1.value;
if(trim(a)){
window.alert('输入不可为空');
document.form1.t1.focus();
return false;
}
}
</script>
<form name='form1' id='form1' method='post' onsubmit='return adjust()'>
<input>...
</form>