onsubmit提交前先验证（验证不通过阻止form提交）

<form onsubmit = "return val();">

<input type="submit" value="提交"/>

</form>

<script type="text/javascript">
function val() {
var beginTime = document.getElementById("beginTime").value;
var endTime = document.getElementById("endTime").value;
var begin = new Date(beginTime.replace(/-/g, "/"));
var end = new Date(endTime.replace(/-/g, "/"));
//js判断日期
if (begin - end > 0) {
$(".error").text("开始时间要在结束时间之前!");
$("#beginTime").css("border", "1px solid red");
$("#endTime").css("border", "1px solid red");
return false;
}
return true;
}
</script>