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。

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