jquery.slices.js

(function($){
	$.fn.extend({
		unslice: function(min, max){
			/* returns a jQuery object containing whatever elements 
			   would've been ditched if we'd done a slice() with the same parameters */
			if ($(this).length && min !== undefined){
				var before = min > 0 ? $(this).slice(0, min) : {};
				var after  = max !== undefined ? $(this).slice(max) : {};
				return $(this).pushStack(after.add(before), "unslice");
			}
		},
		continualSlice: function(min, max, un){
			// like slice, but wraps round the array rather than truncating at the end. 
			// fails if min and max are further apart than the length.
			
			//if un is true it returns whatever isn't between min and max
			var length = $(this).length;
			if (length && min !== undefined && max !== undefined && max - min <= length){
				//if it's entirely out-of-bounds, bring it in so it crosses the end
				while (min < 0)       {max += length; min += length}
				while (min >= length) {max -= length; min -= length}
				//it now or always was entirely in bounds, just a normal slice
				if (max <= length) {
					if (un){ return $(this).pushStack($(this).unslice(min, max));
					} else { return $(this).pushStack($(this).slice(min, max));}
				}
				if (un){ return $(this).pushStack($(this).slice(max, min));
				} else { var end   = $(this).slice(min);
						 var start = $(this).slice(0, max-length);
						 return $(this).pushStack(end.concat(start), "continualSlice");
				}
			}
		},
		continualUnslice: function(min, max) {
			// I intended this to be a separate method, but they're just so damn similar.
			return $(this).continualSlice(min, max, true);
		}
});
})(jQuery);