<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>About</title>
<script src="http://code.jquery.com/jquery-1.8.3.js"></script>
<script type="text/javascript">
$(function(){
$("select[name=mode]").bind("change",function(){
if($(this).val()=="1"){
$("#hykh_lk").show();
}else{
$("#hykh_lk").hide();
}
});
});
</script>
</head>
<body>
<select name="mode" id="mode" class="dept_select" style="width: 100px;"">
<option value="1">离场车辆</option>
<option value="2">进场车辆</option>
<option value="3">滞留车辆</option>
</select>
<input type="text" name="hykh_lk" id="hykh_lk" value="124" style="width: 100px;" class="text"/>
</body>
</html>
原文：http://www.cnblogs.com/mm-happy/p/4649028.html