Get list of CSS Classes in StyleSheet using javascript/jQuery

Question

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How can you determine if a css class exists with Javascript?

Is there a way to check if there is a class named 'some-class-name' in css?

For example, I have:

<style type="text/css">
    .box {
        position: absolute;
        left: 150%;
    }
</style>

My intention is to randomly assign a class to a div on certain event:

var classList = []; //Need to populate this array
$('#updateClass').on('click', function() {
    $('#resultDiv').attr('class',classList[Math.floor((Math.random()*classList.length)+1)]);
});

Is it possible to check by JS/jQuery whether a class named 'box' exists in the stylesheet?

I referred to This Question - How can you determine if a css class exists with Javascript?, But the answer didn't help me because the link in the answer doesn't exists anymore.

Thanks.

check this answers: http://stackoverflow.com/questions/983586/how-can-you-determine-if-a-css-class-exists-with-javascript — silly, Dec 19 '12 at 07:45
`if ($('.validation-errors').length){ /*your code here */ }` but i suspect it will check element has class ?? — NullPoiиteя, Dec 19 '12 at 07:46
Is there any reason for you to check for class names in css? — Spoike, Dec 19 '12 at 07:46
@silly I read that as whats the "season", the winter bash is getting to me — NimChimpsky, Dec 19 '12 at 07:53
Perhaps you should consider using the [data attribute](http://api.jquery.com/data/). — JJJ, Dec 19 '12 at 07:55
Exists in the document, or is specified in the stylesheet(s)? — David Thomas, Dec 19 '12 at 07:59
Just because the answer didn't help you doesn't make it less of a duplicate. You need to explain how your question differs from that one. Not the answers. — BoltClock, Dec 20 '12 at 04:04
I said **question**, not **answer**. You can always place a bounty on the other question if it is similar to what you're looking for; otherwise you need to explain how your question is different from the other one that it should not be closed as a duplicate. — BoltClock, Dec 20 '12 at 04:30

score 1 · Answer 1 · edited May 23 '17 at 10:24

As mentioned above (How can you determine if a css class exists with Javascript?), you could scan the complete CSS for the requested class, or you could add the requested class to an element and check if the attriubtes of the class apply to it. For example:

document.getElementById('yourTestElementID').className=newClass;
if(document.getElementById('yourTestElementID').style.position === 'thevalue' ) {
  // class exists....
}

score -2 · Answer 2 · edited Dec 20 '12 at 04:04

-2

Your random algorithm:

Math.floor((Math.random()*classList.length)+1)

will generate random number from specific range or more generally from 1 to classList.length.

You just need to be sure that the class names that you are going to use and will be populated in the array will exists.

edited Dec 20 '12 at 04:04

BoltClock

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answered Dec 19 '12 at 08:07

gotqn

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Get list of CSS Classes in StyleSheet using javascript/jQuery

2 Answers2