判断是否输入完毕再激活提交按钮

<script language=”javascript”>
function check(){
s.disabled=(t1.value==”"||t2.value==”"||t3.value==”")
}
</script>
<input name=”t1″ onpropertychange=”check()” />
<input name=”t2″ onpropertychange=”check()” />
<input name=”t3″ onpropertychange=”check()” />
<input type=”submit” name=”s” disabled=”desabled” />