Someone

<script>
	// zig zag vertical motion with horizontal movement
	function runimation() {
		var i = 0;
		var obj = someObject;
		
		function part1 () {
			obj.x++;
			obj.y+=2;
		
			setTimeout(part2, 100);
		}
		
		function part2 () {
			obj.x++;
			obj.y-=2;
			
			i++; if (i<400) {
				setTimeout(part1, 100);
			}
		}
	}
</script>


<script>
	function runimation() {
		var i = 0;
		var obj = someObject;
		
		for (var i = 0; i < 400; i++) {
			obj.x++;
			obj.y+=2;
			
			sleep(100);		
			
			obj.x++;
			obj.y-=2;
			
			sleep(100);
		}
	}
</script>