javascript---在*落体实现

实现一些简单的物业*落体需要理解：

clientHeight：浏览器客户机的整体高度

offsetHeight：物（实例div）高低

offsetTop：从对象client最顶层的距离

简单demo例如以下：

<!doctype html>

<html lang="en">

<head>

	<meta charset="UTF-8">

	<title>free_movement</title>

	<style type="text/css">

		#div1{

			position: absolute;

			height: 100px;

			width: 100px;

			background: red;

		}

	</style>

	<script type="text/javascript">

		window.onload=function  () {

			var btn=document.getElementById('btn');

			var div1=document.getElementById('div1');

			var Time=null;

			var speed=0;

			btn.onclick=function () {

				startMove();

			}

			function startMove () {

				clearInterval(Time);

				Time=setInterval(function(){

					speed+= 3;

					var T = div1.offsetTop + speed;

					if(T > document.documentElement.clientHeight - div1.offsetHeight){

						T = document.documentElement.clientHeight - div1.offsetHeight;

						speed *= -1;

						speed *= 0.75;

					}

					div1.style.top=T+'px';

				}, 30)

			}

		}

	</script>

</head>

<body>

	<input type='button' value='開始运动' id="btn">

	<div id="div1"></div>

</body>

</html>

注：clearTnterval(Time)://防止多个点击事件

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javascript---在*落体实现

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