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What is the "hasClass" function with plain JavaScript?

Sophia Hammond |

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

<body>

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

2

14 Answers

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

5

You can check whether element.className matches /\bthatClass\b/.
\b matches a word break.

Or, you can use jQuery's own implementation:

var className = " " + selector + " ";
if ( (" " + element.className + " ").replace(/[\n\t]/g, " ").indexOf(" thatClass ") > -1 )

To answer your more general question, you can look at jQuery's source code on github or at the source for hasClass specifically in this source viewer.

7

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);
}
// 1. Use if for see that classes:
if (document.querySelector(".section-name").classList.contains("section-filter")) { alert("Grid section"); // code...
}
<!--2. Add a class in the .html:-->
<div>...</div>
4

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:

4

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();
};

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

3

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.

7

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!

Use something like:

Array.prototype.indexOf.call(myHTMLSelector.classList, 'the-class');
3 
if (document.body.className.split(/\s+/).indexOf("thatClass") !== -1) { // has "thatClass"
}

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
};
3

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; } }
}
1

What do you think about this approach?

<body> </body>
var bodyClasses = document.querySelector('body').className;
var myClass = new RegExp("thatClass");
var trueOrFalse = myClass.test( bodyClasses );
1

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