rl.jpg
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
#div1 {
width: 100px;
height: 100px;
background: red;
position: absolute;
left: 0;
top: 50px;
}
</style>
<script>
window.onload=function(){
var oDiv=document.getElementById('div1');
var oBtn = document.getElementById('btn1');
oBtn.onclick=function(){
startMove();
};
};
function startMove(){
var oDiv=document.getElementById('div1');
setInterval(function (){
var speed=(300-oDiv.offsetLeft)/30;
//ceil()向上取整数，物体向右移动时使用。floor()向下取整数,物体向左移动时使用。
speed=speed>0?Math.ceil(speed):Math.floor(speed);
oDiv.style.left=oDiv.offsetLeft+speed+'px';
}, 30);
}
</script>
</head>
<body>
<input id="btn1" type="button" value="开始运动">
<div id="div1"></div>
</body>
</html>
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