JS控制层作圆周运动的方法

本文实例讲述了JS控制层作圆周运动的方法。分享给大家供大家参考，具体如下：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>圆周运动</title>
<script type = "text/javascript">
   window.onload = function(){
    var ctrlBtn = $id("ctrl");
    var isMove = true;
    oM = null;
    ctrlBtn.onclick = function(){
    if(isMove){
    moveByCircle();
    }else{
    clearInterval(oM);
    }
    isMove = !isMove;
    }
   }
   function moveByCircle(){
    var bacL = parseInt($id("clockBac").style.left);
    var bacT = parseInt($id("clockBac").style.top);
    var bacW = parseInt($id("clockBac").style.width);
    var bacH = parseInt($id("clockBac").style.height);
    var initL = bacL+bacW/2;
    var initT = bacT+bacH/2;
    var step = 0;
    var r = 65;
    $id("tt").style.left = initL+"px";
    $id("tt").style.top = initT+"px";
    var l = parseInt($id("tt").style.left);
    var t = parseInt($id("tt").style.top);
    oM = window.setInterval(function(){
     if (step == 360) {
      step = 1;
     }
     $id("tt").style.left = (l + r * Math.sin(step)) + "px";
     $id("tt").style.top = (t - r * Math.cos(step)) + "px";
     step += 3.14/30;
      var d = new Date();
      var hh = d.getHours();
      var mm = d.getMinutes();
      var ss = d.getSeconds();
      $id("ctrl").value = hh+":"+mm+":"+ss;
    }, 1000);
   }
   function $id(id){
    return document.getElementById(id);
   }
</script>
</head>
<body>
<div id = "tt" style ="width:10px;height:10px;background:red;position:absolute;top:105px;left:130px;"></div>
<input type = "button" id = "ctrl" style = "width:100px;position:absolute;"/>
<img src = "../img/clock.jpg" id = "clockBac" style ="width:200px;height:200px;top:100px;left:100px;position:absolute;z-index:-999"/>
</body>
</html>

更多关于JavaScript相关内容感兴趣的读者可查看本站专题：《JavaScript切换特效与技巧总结》、《JavaScript查找算法技巧总结》、《JavaScript动画特效与技巧汇总》、《JavaScript错误与调试技巧总结》、《JavaScript数据结构与算法技巧总结》、《JavaScript遍历算法与技巧总结》及《JavaScript数学运算用法总结》

希望本文所述对大家JavaScript程序设计有所帮助。