Edit in JSFiddle

var my_canvas = document.createElement('canvas');
			my_canvas.width = 500;
			my_canvas.height = 300;
			document.body.appendChild(my_canvas);
			var ctx = my_canvas.getContext('2d');
			var x = 20; 
			var y = 20;
			var fps = 60;
			
			
			animacja();
			
			function animacja(){
				requestAnimationFrame( animacja )
				x = x+2;
				y = y+1.4;
				ctx.fillStyle='#38ccdd';
				ctx.fillRect(x+30, y+30, 100, 100);
        ctx.fill();
			}

<script>
</script>