jQuery counting elements by class - what is the best way to implement this?

410
votes

What I'm trying to do is to count all of the elements in the current page with the same class and then I'm going to use it to be added onto a name for an input form. Basically I'm allowing users to click on a <span> and then by doing so add another one for more of the same type of items. But I can't think of a way to count all of these simply with jQuery/JavaScript.

I was going to then name the item as something like name="whatever(total+1)", if anyone has a simple way to do this I'd be extremely grateful as JavaScript isn't exactly my native tongue.

6
javascriptjquerycsselement
the first person i saw got it and i didn't know it was a simple $('.classname').length to get it. If i had more to give i would. Didn't think to try it like that. I've been setting variables quite a bit and simple things like appending documents etc. etc. Wow i feel pretty dumb now i should've thought to look for the .length() command to see what it said... thanks to everyone btw. – 133794m3r
+1 For asking a question like Yoda – jbnunn
@jbnunn what is Yoda? – shasi kanth

6 Answers

750
votes

Should just be something like:

// Gets the number of elements with class yourClass
var numItems = $('.yourclass').length



As a side-note, it is often beneficial to check the length property before chaining a lot of functions calls on a jQuery object, to ensure that we actually have some work to perform. See below:

var $items = $('.myclass');
// Ensure we have at least one element in $items before setting up animations
// and other resource intensive tasks.
if($items.length)
{
  $items.animate(/* */)
    // It might also be appropriate to check that we have 2 or more
    // elements returned by the filter-call before animating this subset of 
    // items.
    .filter(':odd')
      .animate(/* */)
      .end()
    .promise()
    .then(function () { 
       $items.addClass('all-done');
    });
}
23
votes

Getting a count of the number of elements that refer to the same class is as simple as this

<html>
    <head>
        <script src="http://code.jquery.com/jquery-1.4.2.min.js"></script>
        <script type="text/javascript">

            $(document).ready(function() {
                alert( $(".red").length );
            });

        </script>
    </head>
    <body>

        <p class="red">Test</p>
        <p class="red">Test</p>
        <p class="red anotherclass">Test</p>
        <p class="red">Test</p>
        <p class="red">Test</p>
        <p class="red anotherclass">Test</p>
    </body>
</html>
16
votes
var count = $('.' + myclassname).length;
9
votes

for counting:

$('.yourClass').length;

should work fine.

storing in a variable is as easy as:

var count = $('.yourClass').length;

6
votes

HTML:

<div>
    <img src='' class='class' />
    <img src='' class='class' />
    <img src='' class='class' />
</div>

JavaScript:

var numItems = $('.class').length; 
        
alert(numItems);

Fiddle demo for inside only div

4
votes

try

document.getElementsByClassName('myclass').length


let num = document.getElementsByClassName('myclass').length;
console.log('Total "myclass" elements: '+num);
.myclass { color: red }
<span class="myclass" >1</span>
<span>2</span>
<span class="myclass">3</span>
<span class="myclass">4</span>