<body>
<div id="ball" style="width:20px; height:20px; background:red; border-radius:50%; position:absolute; left:0; top:80px;"></div> <script> var ball = document.getElementById("ball"); var radian = 0.1; var x = 0; var y = 0; document.onmousemove = function(e){ e = e || event; x = e.clientX; y = e.clientY; } var timer1 = setInterval(function(){ ball.style.left = x + Math.cos(radian) * 80 + "px"; ball.style.top = y + Math.sin(radian) * 80 + "px"; radian+=0.1; },20); </script></body>