demo示例:
<form onsubmit="return login()">
<input type="text"name="name" required="required" />
<input type="password" name="userpwd" autocomplete="off" required="required" />
<button type="submit">登录</button>
</form>
当点击登录时候,触发login方法,在该方法中需要返回false/true,若是返回false,则相当于
<form onsubmit="return false">
<input type="text"name="name" required="required" />
<input type="password" name="userpwd" autocomplete="off" required="required" />
<button type="submit">登录</button>
</form>
该submit操作不会进行。