2157
votes

I want to select all the elements that have the two classes a and b.

<element class="a b">

So, only the elements that have both classes.

When I use $(".a, .b") it gives me the union, but I want the intersection.

14
It would be nice if you could define what union and intersection means for us newbs :)Kellen Stuart
@KolobCanyon union and intersection are basic set theory concepts. So for instance a union would be all French speakers (includes both men and women), whereas an intersection would be all women who speak French (excludes everyone who does not speak French, and excludes all people who are not women). Unions and intersections can be made with any number of characteristics defining each set. en.wikipedia.org/wiki/Union_(set_theory) en.wikipedia.org/wiki/Intersection_(set_theory)Katharine Osborne
I think you mean that of the two sets "women" and "French-speakers", the union would be all the women in the world and all the French-speakers in the world, a set that includes both women who don't speak French and French-speaking men. The intersection is, as you wrote, only those women who speak French.Teemu Leisti

14 Answers

2749
votes

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')

The order is not relevant, so you can also swap the classes:

$('.b.a')

So to match a div element that has an ID of a with classes b and c, you would write:

$('div#a.b.c')

(In practice, you most likely don't need to get that specific, and an ID or class selector by itself is usually enough: $('#a').)

177
votes

You can do this using the filter() function:

$(".a").filter(".b")
128
votes

For the case

<element class="a">
  <element class="b c">
  </element>
</element>

You would need to put a space in between .a and .b.c

$('.a .b.c')
67
votes

The problem you're having, is that you are using a Group Selector, whereas you should be using a Multiples selector! To be more specific, you're using $('.a, .b') whereas you should be using $('.a.b').

For more information, see the overview of the different ways to combine selectors herebelow!


Group Selector : ","

Select all <h1> elements AND all <p> elements AND all <a> elements :

$('h1, p, a')

Multiples selector : "" (no character)

Select all <input> elements of type text, with classes code and red :

$('input[type="text"].code.red')

Descendant Selector : " " (space)

Select all <i> elements inside <p> elements:

$('p i')

Child Selector : ">"

Select all <ul> elements that are immediate children of a <li> element:

$('li > ul')

Adjacent Sibling Selector : "+"

Select all <a> elements that are placed immediately after <h2> elements:

$('h2 + a')

General Sibling Selector : "~"

Select all <span> elements that are siblings of <div> elements:

$('div ~ span')
40
votes

$('.a .b , .a .c').css('border', '2px solid yellow');
//selects b and c
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div class="a">a
  <div class="b">b</div>
  <div class="c">c</div>
  <div class="d">d</div>
</div>
25
votes

Just mention another case with element:

E.g. <div id="title1" class="A B C">

Just type: $("div#title1.A.B.C")

25
votes

Vanilla JavaScript solution:-

document.querySelectorAll('.a.b')

20
votes

For better performance you can use

$('div.a.b')

This will look only through the div elements instead of stepping through all the html elements that you have on your page.

9
votes

Group Selector

body {font-size: 12px; }
body {font-family: arial, helvetica, sans-serif;}
th {font-size: 12px; font-family: arial, helvetica, sans-serif;}
td {font-size: 12px; font-family: arial, helvetica, sans-serif;}

Becomes this:

body, th, td {font-size: 12px; font-family: arial, helvetica, sans-serif;}

So in your case you have tried the group selector whereas its an intersection

$(".a, .b") 

instead use this

$(".a.b") 
4
votes

your code $(".a, .b") will work for below multiple elements (at a same time)

<element class="a">
<element class="b">

if you want to select element having a and b both class like <element class="a b"> than use js without coma

$('.a.b')
3
votes

You do not need jQuery for this

In Vanilla you can do :

document.querySelectorAll('.a.b')
2
votes

You can use getElementsByClassName() method for what you want.

var elems = document.getElementsByClassName("a b c");
elems[0].style.color = "green";
console.log(elems[0]);
<ul>
  <li class="a">a</li>
  <li class="a b">a, b</li>
  <li class="a b c">a, b, c</li>
</ul>

This is the fastest solution also. you can see a benchmark about that here.

1
votes

var elem = document.querySelector(".a.b");

1
votes

Below example will give you idea about to select at a time multiple nested class selectors and direct class selectors in one line

//Here is Explaination of Selectors  
//.a .b .c  = selects nested child c which is inside of div a and b
//.a .d     = selects nested child d which is inside of div a 
//.f        = selects direct element ie div f which is outside of div a and b
$('.a .b .c , .a .d, .f').css('background-color', 'grey');
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div class="a">a
  <div class="b">b
       <div class="c">c</div>
  </div> 
  <div class="d">d</div>
</div>
<div class="e">e</div>
<div class="f">f</div>