type="button"和Submit剖析

代码示例:

<script type="text/javascript">
function sendEmail(){
?var email = document.f.email.value;
?if(email==""){
??alert("收邮件地址不能为空！");
??document.f.email.focus();
??return;
?}
?document.all('editLink').href = "<%=request.getContextPath() %>/mail/sendEmail?email="+email;
?document.all('editLink').click();
}
</script>

<form name="f" action="" method="post">
<a id="editLink" href="aa" style="display:none"></a>

<input name="Submit" type="button" value="提交" onclick="return sendEmail()" />

剖析:提交按钮type="Submit"会执行两次提交操作

第一次:执行form的action提交

第二次:执行onclick中调用的函数sendEmail里面的提交