hasClass在我的js代码中不起作用? [英] hasClass doesn't work in my js code?

问题描述

我想在以下代码中使用hasClass，但这对我不起作用，请在jsfiddle中查看我的演示并告诉我，我该怎么做?

I want to use hasClass in the following code, but that doesn't work for me, please see my demo in jsfiddle and tell me, what do I do wrong?

<span>
    <input type="text" name="relation" class="IdRelation">
</span>
​

if ($('span').hasClass('IdRelation')) {
  alert("ok");
}​

演示

推荐答案

解决方案

该类位于<span>子级(<input>)上，因此将其添加到jQuery选择器中:$('span input').

Solution

The class is on the <span> child, an <input>, so add it in the jQuery selector : $('span input').

if ($('span input').hasClass('IdRelation')) {
  alert('ok');
}​

尝试演示.

根据jQuery文档，$('span input')是 后代选择器 :

Accorting to jQuery documentation, $('span input') is a descendant selector :

选择作为给定祖先的后代的所有元素.

Selects all elements that are descendants of a given ancestor.

您也可以使用$('span > input').这是 子选择器 :

You could also use $('span > input'). It is a child selector :

选择父"指定的元素的子"指定的所有直接子元素.

Selects all direct child elements specified by "child" of elements specified by "parent".

两种情况都对您有利，因为input是<span>的直接子代.

Both are good in your situation, because the input is a direct child of the <span>.

如果您的代码是:

<div>
    <form>
        <input type="text" name="relation" class="IdRelation">
    </form>
</div>

解决方案将为$('div input')或$('div > form > input').

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