Javascript: Keyboard navigation control, Vertically

gistfile1.txt

// --------- keyboard navigation control --------- //
var isinmotion = false;
$j(document).keydown(function(e){
	switch (e.keyCode) {
		case 38:
			//console.log("up");
			if (isinmotion) {
				return false;
			} else { 
				var curr = $j("li.viewing:last");
				var prev = curr.prev("li");
				if(prev.size() > 0 ) {
					isinmotion = true;

					$j(window).scrollTo( prev, 800, {easing:'swing', onAfter:function(){
						isinmotion = false;
					}});
				}
			}
			return false;
		break;

		case 40:
			//console.log("down");
			if (isinmotion) {
				return false;
			} else {
				var curr = $j("li.viewing:last");
				var next = curr.next("li");
				if(next.size() > 0) {
					isinmotion = true;
					$j(window).scrollTo( next, 800, {easing:'swing', onAfter:function(){
						isinmotion = false;
					}});
				}
			}
			return false;
		break;
	}
});