如何在jQuery中选择具有多个类的元素？
我想选择所有具有两个类 a 和 b 的元素。
I want to select all the elements that have the two classes a and b.
<element class="a b">
因此，只有两个类的元素。
当我使用 $（。a，.b）时，它给了我联盟，但我想要交集。
When I use $(".a, .b") it gives me the union, but I want the intersection.
如果你只想匹配两个类的元素（交集，就像逻辑AND） ，只需将选择器一起写成不含空格：
If you want to match only elements with both classes (an intersection, like a logical AND), just write the selectors together without spaces in between:
$('.a.b')
订单不相关，所以你也可以交换这些类：
The order is not relevant, so you can also swap the classes:
$('.b.a')
所以要匹配一个 div 元素，其元素 a ，类 b 和 c ，你会写：
So to match a div element that has an ID of a with classes b and c, you would write:
$('div#a.b.c')
（实际上，你很可能不喜欢不需要特定的，并且ID或类选择器本身就足够了： $（'＃a' ）。）
(In practice, you most likely don't need to get that specific, and an ID or class selector by itself is usually enough: $('#a').)