a.ScrollTop calculation;
b. Positioning value calculation of scroll element;
c. Scroll cycle setting;
The code is as follows:
css part:
/*测试用的高度*/ body{ height:3000px;} div,ul,li,body{margin:0; padding:0;} /*position:absolute;用于元素的定位*/ #roll{width:50px; height:100px; background:#99CC00; position:absolute;}
Html code:
<body> <div id="roll"></div> </body>
JS code:
var roll=document.getElementById('roll'), initX=0, initY, compY, sp=15, //可调整时间间隔,步进值不宜过大,不然IE下有点闪屏; timeGap=5, doc=document.documentElement, docBody=document.body; compY=initY=200; roll.style.right=initX+"px"; ;(function(){ var curScrollTop=(doc.scrollTop||docBody.scrollTop||0)-(doc.clientTop||docBody.clientTop||0); //每次comP的值都不一样;直到roll.style.top===doc.scrollTop+initY; compY+=(curScrollTop+initY-compY)/sp; roll.style.top=Math.ceil(compY)+"px"; setTimeout(arguments.callee,timeGap); })();
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