[javascript] What is the "hasClass" function with plain JavaScript?

How do you do jQuery’s hasClass with plain ol’ JavaScript? For example,

<body class="foo thatClass bar">

What’s the JavaScript way to ask if <body> has thatClass?

This question is related to javascript dom

The answer is


Use something like:

Array.prototype.indexOf.call(myHTMLSelector.classList, 'the-class');

The most effective one liner that

  • returns a boolean (as opposed to Orbling's answer)
  • Does not return a false positive when searching for thisClass on an element that has class="thisClass-suffix".
  • is compatible with every browser down to at least IE6

function hasClass( target, className ) {
    return new RegExp('(\\s|^)' + className + '(\\s|$)').test(target.className);
}

Well all of the above answers are pretty good but here is a small simple function I whipped up. It works pretty well.

function hasClass(el, cn){
    var classes = el.classList;
    for(var j = 0; j < classes.length; j++){
        if(classes[j] == cn){
            return true;
        }
    }
}

hasClass function:

HTMLElement.prototype.hasClass = function(cls) {
    var i;
    var classes = this.className.split(" ");
    for(i = 0; i < classes.length; i++) {
        if(classes[i] == cls) {
            return true;
        }
    }
    return false;
};

addClass function:

HTMLElement.prototype.addClass = function(add) {
    if (!this.hasClass(add)){
        this.className = (this.className + " " + add).trim();
    }
};

removeClass function:

HTMLElement.prototype.removeClass = function(remove) {
    var newClassName = "";
    var i;
    var classes = this.className.replace(/\s{2,}/g, ' ').split(" ");
    for(i = 0; i < classes.length; i++) {
        if(classes[i] !== remove) {
            newClassName += classes[i] + " ";
        }
    }
    this.className = newClassName.trim();
};

Here is the simplest way Only with javascript:

var allElements = document.querySelectorAll('*');
for (var i = 0; i < allElements.length; i++) {
    if (allElements[i].hasAttribute("class")) {
         //console.log(allElements[i].className);
         if (allElements[i].className.includes("_the _class ")) { 
              console.log("I see the class");
         }
    }
}

a good solution for this is to work with classList and contains.

i did it like this:

... for ( var i = 0; i < container.length; i++ ) {
        if ( container[i].classList.contains('half_width') ) { ...

So you need your element and check the list of the classes. If one of the classes is the same as the one you search for it will return true if not it will return false!


The attribute that stores the classes in use is className.

So you can say:

if (document.body.className.match(/\bmyclass\b/)) {
    ....
}

If you want a location that shows you how jQuery does everything, I would suggest:

http://code.jquery.com/jquery-1.5.js


What do you think about this approach?

<body class="thatClass anotherClass"> </body>

var bodyClasses = document.querySelector('body').className;
var myClass = new RegExp("thatClass");
var trueOrFalse = myClass.test( bodyClasses );

https://jsfiddle.net/5sv30bhe/


Element.matches()

Instead of $(element).hasClass('example') in jQuery, you can use element.matches('.example') in plain JavaScript:

if (element.matches('.example')) {
  // Element has example class ...
}

View Browser Compatibility


Simply use classList.contains():

if (document.body.classList.contains('thatClass')) {
    // do some stuff
}

Other uses of classList:

document.body.classList.add('thisClass');
// $('body').addClass('thisClass');

document.body.classList.remove('thatClass');
// $('body').removeClass('thatClass');

document.body.classList.toggle('anotherClass');
// $('body').toggleClass('anotherClass');

Browser Support:

  • Chrome 8.0
  • Firefox 3.6
  • IE 10
  • Opera 11.50
  • Safari 5.1

classList Browser Support


This 'hasClass' function works in IE8+, FireFox and Chrome:

hasClass = function(el, cls) {
    var regexp = new RegExp('(\\s|^)' + cls + '(\\s|$)'),
        target = (typeof el.className === 'undefined') ? window.event.srcElement : el;
    return target.className.match(regexp);
}

[Updated Jan'2021] A better way:

hasClass = (el, cls) => {
  [...el.classList].includes(cls); //cls without dot
};

I use a simple/minimal solution, one line, cross browser, and works with legacy browsers as well:

/\bmyClass/.test(document.body.className) // notice the \b command for whole word 'myClass'

This method is great because does not require polyfills and if you use them for classList it's much better in terms of performance. At least for me.

Update: I made a tiny polyfill that's an all round solution I use now:

function hasClass(element,testClass){
  if ('classList' in element) { return element.classList.contains(testClass);
} else { return new Regexp(testClass).exec(element.className); } // this is better

//} else { return el.className.indexOf(testClass) != -1; } // this is faster but requires indexOf() polyfill
  return false;
}

For the other class manipulation, see the complete file here.


if (document.body.className.split(/\s+/).indexOf("thatClass") !== -1) {
    // has "thatClass"
}

_x000D_
_x000D_
// 1. Use if for see that classes:_x000D_
_x000D_
if (document.querySelector(".section-name").classList.contains("section-filter")) {_x000D_
  alert("Grid section");_x000D_
  // code..._x000D_
}
_x000D_
<!--2. Add a class in the .html:-->_x000D_
_x000D_
<div class="section-name section-filter">...</div>
_x000D_
_x000D_
_x000D_