Check if an element contains a class in JavaScript?

Solution 1:

Use element.classList .contains method:

element.classList.contains(class);

This works on all current browsers and there are polyfills to support older browsers too.

Alternatively, if you work with older browsers and don't want to use polyfills to fix them, using indexOf is correct, but you have to tweak it a little:

function hasClass(element, className) {
    return (' ' + element.className + ' ').indexOf(' ' + className+ ' ') > -1;
}

Otherwise you will also get true if the class you are looking for is part of another class name.

DEMO

jQuery uses a similar (if not the same) method.

Applied to the example:

As this does not work together with the switch statement, you could achieve the same effect with this code:

var test = document.getElementById("test"),
    classes = ['class1', 'class2', 'class3', 'class4'];

test.innerHTML = "";

for(var i = 0, j = classes.length; i < j; i++) {
    if(hasClass(test, classes[i])) {
        test.innerHTML = "I have " + classes[i];
        break;
    }
}

It's also less redundant ;)

Solution 2:

The easy and effective solution is trying .contains method.

test.classList.contains(testClass);

Solution 3:

In modern browsers, you can just use the contains method of Element.classList :

testElement.classList.contains(className)

Demo

var testElement = document.getElementById('test');

console.log({
    'main' : testElement.classList.contains('main'),
    'cont' : testElement.classList.contains('cont'),
    'content' : testElement.classList.contains('content'),
    'main-cont' : testElement.classList.contains('main-cont'),
    'main-content' : testElement.classList.contains('main-content')
});

<div id="test" class="main main-content content"></div>

Supported browsers

(from CanIUse.com)

Polyfill

If you want to use Element.classList but you also want to support older browsers, consider using this polyfill by Eli Grey.

Solution 4:

Element.matches()

element.matches(selectorString)

According to MDN Web Docs:

The Element.matches() method returns true if the element would be selected by the specified selector string; otherwise, returns false.

Therefore, you can use Element.matches() to determine if an element contains a class.

const element = document.querySelector('#example');

console.log(element.matches('.foo')); // true

<div id="example" class="foo bar"></div>

View Browser Compatibility