jQuery-object.id在未定义时未定义 [英] JQuery - object.id is undefined when it shouldn't be

问题描述

我正在使用JQuery，却遇到了这个奇怪的(也许是愚蠢的)错误.

I'm working with JQuery and i'm running into this strange (or perhaps stupid) error.

在我的HTML中，我有:

In my HTML I have:

<input type="password" name="repeatPassword" id="id_repeatPassword" /> 

然后在我的JavaScript代码中，我有:

And then in my javascript code i have:

validateRepeatPassword($('#id_repeatPassword'));

不幸的是在函数"validateRepeatPassword"中:

Unfortunately in the function "validateRepeatPassword":

function validateRepeatPassword(o) {
        // this works
        if (o.value == $("#id_password").val()) {
        // this returns "undefined"
        alert(o.id)
...
}

为什么?

推荐答案

o是对jQuery对象的引用，而不是DOM元素引用.在您的validateRepeatPassword函数内部，执行以下操作:

o is a reference to a jQuery object, NOT a DOM element reference. Inside your validateRepeatPassword function do:

alert( $(o).attr('id') );

如果要从jQuery对象访问直接DOM元素的属性，

If you want to access the direct DOM element's property from the jQuery object,

alert( o[0].id )

alert( o.get(0).id );

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