Add a class to a DIV with javascript

Question

Example HTML:

How can I add the class class_two without replacing

Answer 1

You can make life easier with a couple of helper functions:

function addClass(el, className) {
  var classes = el.className.match(/\S+/g) || [];  

  if (!hasClass(el, className)) {
    classes.push(className);
  }
  el.className = classes.join(' ');
}

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

addClass(document.getElementById('foo'), 'bar')

Answer 2

You may use jQuery.

$('#YourElement').addClass('YourClass'); //add

$('#YourElement').removeClass('YourClass'); //remove

$('#YourElement').toggleClass('YourClass'); //toggle

---

Or Javascript, if you wish.

document.getElementById('id').classList.add('YourClass'); //add
document.getElementById('id').classList.remove('YourClass'); //remove

Answer 3

Standard javascript:

document.getElementById('foo').className += ' class_two'

// Or see deekshith's answer below if you only need to support new browsers

or JQuery:

$('#foo').addClass('class_two');

Answer 4

A better way to add a class would be to use Element.classList.add():

document.getElementById('foo').classList.add("class_two");