Check if class already assigned before adding

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:

<

Answer 1

A simple check in the console would have told you that calling addClass multiple times with the same class is safe.

Specifically you can find the check in the source

if ( !~setClass.indexOf( " " + classNames[ c ] + " " ) ) {
  setClass += classNames[ c ] + " ";
}