Check if an element contains a class in JavaScript?

Question

Using plain JavaScript (not jQuery), Is there any way to check if an element contains a class?

Currently, I\'m doing this:

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Answer 1

See this Codepen link for faster and easy way of checking an element if it has a specific class using vanilla JavaScript~!

hasClass (Vanilla JS)

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

Answer 2

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

Answer 3

I've created a prototype method which uses classList, if possible, else resorts to indexOf:

Element.prototype.hasClass = Element.prototype.hasClass || 
  function(classArr){
    var hasClass = 0,
        className = this.getAttribute('class');
  
    if( this == null || !classArr || !className ) return false;
  
    if( !(classArr instanceof Array) )
      classArr = classArr.split(' ');

    for( var i in classArr )
      // this.classList.contains(classArr[i]) // for modern browsers
      if( className.split(classArr[i]).length > 1 )  
          hasClass++;

    return hasClass == classArr.length;
};


///////////////////////////////
// TESTS (see browser's console when inspecting the output)

var elm1 = document.querySelector('p');
var elm2 = document.querySelector('b');
var elm3 = elm1.firstChild; // textNode
var elm4 = document.querySelector('text'); // SVG text

console.log( elm1, ' has class "a": ', elm1.hasClass('a') );
console.log( elm1, ' has class "b": ', elm1.hasClass('b') );
console.log( elm1, ' has class "c": ', elm1.hasClass('c') );
console.log( elm1, ' has class "d": ', elm1.hasClass('d') );
console.log( elm1, ' has class "a c": ', elm1.hasClass('a c') );
console.log( elm1, ' has class "a d": ', elm1.hasClass('a d') );
console.log( elm1, ' has class "": ', elm1.hasClass('') );

console.log( elm2, ' has class "a": ', elm2.hasClass('a') );

// console.log( elm3, ' has class "a": ', elm3.hasClass('a') );

console.log( elm4, ' has class "a": ', elm4.hasClass('a') );

<p class='a b c'>This is a <b>test</b> string</p>
<svg xmlns="http://www.w3.org/2000/svg" width="100px" height="50px">
    <text x="10" y="20" class='a'>SVG Text Example</text>
</svg>

Test page

Answer 4

This is supported on IE8+.

First we check if classList exists if it does we can use the contains method which is supported by IE10+. If we are on IE9 or 8 it falls back to using a regex, which is not as efficient but is a concise polyfill.

if (el.classList) {
  el.classList.contains(className);
} else {
  new RegExp('(^| )' + className + '( |$)', 'gi').test(el.className);
}

Alternatively if you are compiling with babel you can simply use: el.classList.contains(className);

Answer 5

I created these functions for my website, I use only vanilla javascript, maybe it will help someone. First I created a function to get any HTML element:

//return an HTML element by ID, class or tag name
    var getElement = function(selector) {
        var elements = [];
        if(selector[0] == '#') {
            elements.push(document.getElementById(selector.substring(1, selector.length)));
        } else if(selector[0] == '.') {
            elements = document.getElementsByClassName(selector.substring(1, selector.length));
        } else {
            elements = document.getElementsByTagName(selector);
        }
        return elements;
    }

Then the function that recieve the class to remove and the selector of the element:

var hasClass = function(selector, _class) {
        var elements = getElement(selector);
        var contains = false;
        for (let index = 0; index < elements.length; index++) {
            const curElement = elements[index];
            if(curElement.classList.contains(_class)) {
                contains = true;
                break;
            }
        }
        return contains;
    }

Now you can use it like this:

hasClass('body', 'gray')
hasClass('#like', 'green')
hasClass('.button', 'active')

Hope it will help.

Answer 6

A simplified oneliner:¹

function hasClassName(classname,id) {
 return  String ( ( document.getElementById(id)||{} ) .className )
         .split(/\s/)
         .indexOf(classname) >= 0;
}

¹ indexOf for arrays is not supported by IE (ofcourse). There are plenty of monkey patches to be found on the net for that.