我喜欢完整的代码呈现,以便于后期的温习
弹力球
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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>弹力球</title>
<style>
body{
margin:0;
padding:0;
}
#box{
width:50px;
height:50px;
background:red;
position:absolute;
left:0;
top:0;
margin:0;
border-radius: 50%;
}
</style>
</head>
<body>
<div id="box"></div>
</body>
<script>
window.onload=function(){
oDiv=document.getElementById('box');
var l=0;
var t=0;
var ispeedX=0;
var ispeedY=0;
var timer=null;
oDiv.onmousedown=function(e){
clearInterval(timer);
var ev=e||event;
//鼠标距离box的外边框的距离
var disX=ev.clientX - oDiv.offsetLeft;
var disY=ev.clientY - oDiv.offsetTop;
document.onmousemove=function(e){
var ev=e||event;
//box的left值
oDiv.style.left= ev.clientX - disX + 'px';
oDiv.style.top=ev.clientY -disY + 'px';
//box下一次距离前一次的移动距离
ispeedX=oDiv.offsetLeft-l;
console.log(ispeedX);
ispeedY=oDiv.offsetTop-t;
//把前一次的boxoffsetLeft值赋给l
l=oDiv.offsetLeft;
console.log(l);
t=oDiv.offsetTop;
}//onmousemove
document.onmouseup=function(){
document.onmousemove=null;
clearInterval(timer);
boomMove(oDiv);
function boomMove(obj){
//获取浏览器可视区域的宽度和高度
var clientX=document.documentElement.clientWidth-obj.offsetWidth||document.body.clientWidth-obj.offsetWidth;
var clientY=document.documentElement.clientHeight-obj.offsetHeight||document.body.clientHeight-obj.offsetHeight;
timer=setInterval(function(){
//每一次移动的top距离相加以获得重力
ispeedY +=3;
// ispeedX +=3;
var x= obj.offsetLeft + ispeedX;
var t= obj.offsetTop + ispeedY;
console.log(ispeedX);
console.log(ispeedY);
if(x>clientX){
x=clientX;
ispeedX *=-0.9;
// ispeedY *=0.8;
};
if(x<0){
x=0;
ispeedX *=-0.9;
// ispeedY *=0.8;
};
if(t>clientY){
t=clientY;
ispeedY *=-0.8;
ispeedX *=0.9;
};
if(t<0){
t=0;
ispeedY *=-1.1;
};
obj.style.left= x + 'px';
obj.style.top= t + 'px';
// Math.abs取绝对值
//ispeedX一直在乘以0.8，数值不会变为0，为了使其为0，做个判断
if(Math.abs(ispeedX)<1){ispeedX=0;};
if(Math.abs(ispeedY)<1){ispeedY=0;};
if(ispeedX==0&&ispeedY==0&&oDiv.offsetTop==clientY){clearInterval(timer); }
},30) ;
}
}//onmouseup
}//onmousedown
}
</script>
</html>