表單form中<button>提交表單

表單中有<button>一旦點擊就會自動提交表單，要給<button>加上type=“button”屬性纔可以

阻止表單提交

<form action="" method="GET" onsubmit = "return login_check()">
	<label for="username">用戶名:</label><br/>
	<input placeholder="用戶名" type="text" name="username" value="" id="username" tabindex="1"/>
	<br/><label for="password">密碼:</label><br/>
	<input placeholder="密碼" type="password" name="password" value="" id="password" tabindex="2" />
	<button type="submit" class="flatbtn-blu"  tabindex="3" >登錄</button>
	<button type="button" class="flatbtn-blu" onclick="showRegist()" tabindex="4" >註冊</button>
</form>

<button type="button" class="flatbtn-blu" onclick="showRegist()" tabindex="4" >註冊</button>

如果沒有type=“button” 註冊按鈕也會提交表單

login_check()返回值爲true時纔會提交表單

function login_check(){
	if(document.getElementById("username").value == ""){
		alert("用戶名不能爲空！");
		return false;
	}
	if(document.getElementById("password").value == ""){
		alert("密碼不能爲空！");
		return false;
	}
	return true;
}