Question

In jQuery, is it recommended to check if a class is already assigned to an element before adding that class? Will it even have any effect at all?

For example:

<label class='foo'>bar</label>

When in doubt if class baz has already been assigned to label, would this be the best approach:

var class = 'baz';
if (!$('label').hasClass(class)) {
  $('label').addClass(class);
}

or would this be enough:

$('label').addClass('baz');

Answer 1

Just call addClass(). jQuery will do the check for you. If you check on your own, you are doubling the work, since jQuery will still run the check for you.