Adds the specified class to each of the set of matched elements with an optional transition between the states.
Arguments:
| class | String | |
|---|---|---|
| One CSS class to add to the elements. | ||
| duration (Optional) | String, Number | |
| A string representing one of the three predefined speeds ("slow", "normal", or "fast") or the number of milliseconds to run the animation (e.g. 1000). | ||