submit中return function()有效的原因

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">登錄</button>
</form>

當點擊登錄時候，觸發login方法，在該方法中需要返回false/true，若是返回false，則相當於

<form onsubmit="return false"> 
    <input type="text"name="name" required="required" /> 
    <input type="password" name="userpwd" autocomplete="off" required="required" /> 
    <button type="submit">登錄</button>
</form>

該submit操作不會進行。

文章參考：https://stackoverflow.com/questions/5195933/with-form-validation-why-onsubmit-return-functionname-instead-of-onsubmit