The .nextOrFirst() jQuery function/plugin detailed here works as an alias for .next(), except when there are no more objects for .next() to select. When this happens, .nextOrFirst() will automatically select the first sibling (essentially treating the first element as “next”).

By itself, .next() is used, not surprisingly, to change any current selection to that selection’s next sibling (you can read more about it here). By default, if .next() is used on the last element within any given parent (for instance, the last <li> in a <ul>), it will return nothing. But what if you want to ensure that .next() always returns a selection? For instance, what if we want to get the first <li> if we reach the last one?

At some point you will run into scripting situations where you’ll need this very functionality – particularly if scripting something that works on a timed loop. To make life easier, use these simple jQuery extensions to automatically select the first item if there’s no .next() left to select.

/********************************************************************************
 * jQuery.nextOrFirst()
 *
 * PURPOSE:  Works like next(), except gets the first item from siblings if there is no "next" sibling to get.
 ********************************************************************************/
jQuery.fn.nextOrFirst = function(selector){
    var next = this.next(selector);
    return (next.length) ? next : this.prevAll(selector).last();
}

Remember that in order to use this function, jQuery must already be loaded. If you need a prevOrLast() function, use this:

/********************************************************************************
 * jQuery.prevOrLast()
 * PURPOSE:
 * Works like prev(), except gets the last item from siblings if there is no "prev" sibling to get.
 ********************************************************************************/
jQuery.fn.prevOrLast = function(selector){
    var prev = this.prev(selector);
    return (prev.length) ? prev : this.nextAll(selector).last();
}