效果预览：
一、模拟抽奖的实现过程
旋转原理：当支持CSS3属性采用transform: rotate（角度deg）设置,当角度为正数时顺时针旋转，当为负数时逆时针旋转。如果是IE8及其以下，采用采用绝对定位设置top和left，模拟角度旋转。
run方法，参数angle指角度
复制代码 代码如下:
function run(angle) {
if (isIE) {
cosDeg = Math.cos(angle * Math.PI / 180);
sinDeg = Math.sin(angle * Math.PI / 180);
with (target.filters.item(0)) {
M11 = M22 = cosDeg; M12 = -(M21 = sinDeg);
}
target.style.top = (orginH - target.offsetHeight) / 2 + "px";
target.style.left = (orginW - target.offsetWidth) / 2 + "px";
} else if (target.style.MozTransform !== undefined) {
target.style.MozTransform = "rotate(" + angle + "deg)";
} else if (target.style.OTransform !== undefined) {
target.style.OTransform = "rotate(" + angle + "deg)";
} else if (target.style.webkitTransform !== undefined) {
target.style.webkitTransform = "rotate(" + angle + "deg)";
} else {
target.style.transform = "rotate(" + angle + "deg)";
}
}
模拟转盘加速，匀速和减速。当角度小于某个数值时，让其处于加速此处采用1.01的系数作为加速度，当大于某个数值时处于高速匀速状态，当角度大于设置的最大数值时，让其减速采用系数为0.99。设置负数作为减速的值（即变量 tmp），随即获取负360中的值（即变量 m），当大于这个值时，转盘停止。
复制代码 代码如下:
var tmp = -900;
var m = -parseInt(Math.random() * 360);
timer = setInterval(function () {
if (i > 3000) {
tmp = parseInt(tmp * 0.99);
if (tmp > m) {
tmp = m;
clearInterval(timer);
msg(m);
}
run(tmp);
}
else if (i > 1000) {
i = i + 45;
run(i);
}
else {
i = parseInt((i + 1) * 1.01);
run(i);
}
}, 50);
启动抽奖和重新设置抽奖
复制代码 代码如下:
<input id="test" type="button" value="抽奖" />
<input id="restart" type="button" value="再抽一次" />
m$('test').onclick = function () {
m$('test').style.display = "none";
showMsg();
}
m$('restart').onclick = function () {
m$('restart').style.display = "none";
if (isIE) {
m$("demo").style.top = "0px";
m$("demo").style.left = "0px";
} else if (m$("demo").style.MozTransform !== undefined) {
m$("demo").style.MozTransform = 'rotate(0deg)';
} else if (m$("demo").style.OTransform !== undefined) {
m$("demo").style.OTransform = 'rotate(0deg)';
} else if (m$("demo").style.webkitTransform !== undefined) {
m$("demo").style.webkitTransform = 'rotate(0deg)';
} else {
m$("demo").style.transform = 'rotate(0deg)';
}
m$('test').style.display = "block";
i = 0;
}
二、完整代码demo:
复制代码 代码如下:<!DOCTYPE html>
<html>
<head>
<title>抽奖</title>
<style type="text/css">
#container{width: 400px;height: 400px;position: relative;margin: 0 auto;}
#demo{position: absolute;filter: progid:DXImageTransform.Microsoft.Matrix(sizingmethod="auto expand");}
</style>
</head>
<body>
<div id="container">
<div id="demo">
<img src="http://files.jb51.net/file_images/article/201406/20146394819279.png" width="400" height="400" />
</div>
</div>
<input id="test" type="button" value="抽奖" />
<input id="restart" type="button" value="再抽一次" />
<div id="msg">
</div>
<script type="text/javascript">
var m$ = function (id) { return document.getElementById(id); }
var ua = navigator.userAgent;
var isIE = /msie/i.test(ua) && !window.opera;
var i = 1, sinDeg = 0, cosDeg = 0, timer = null;
var mRotate = function () {
var rotate = function (target, msg) {
target = m$(target);
var orginW = target.clientWidth, orginH = target.clientHeight;
clearInterval(timer);
function run(angle) {
if (isIE) {
cosDeg = Math.cos(angle * Math.PI / 180);
sinDeg = Math.sin(angle * Math.PI / 180);
with (target.filters.item(0)) {
M11 = M22 = cosDeg; M12 = -(M21 = sinDeg);
}
target.style.top = (orginH - target.offsetHeight) / 2 + "px";
target.style.left = (orginW - target.offsetWidth) / 2 + "px";
} else if (target.style.MozTransform !== undefined) {
target.style.MozTransform = "rotate(" + angle + "deg)";
} else if (target.style.OTransform !== undefined) {
target.style.OTransform = "rotate(" + angle + "deg)";
} else if (target.style.webkitTransform !== undefined) {
target.style.webkitTransform = "rotate(" + angle + "deg)";
} else {
target.style.transform = "rotate(" + angle + "deg)";
}
}
var tmp = -900;
var m = -parseInt(Math.random() * 360);
timer = setInterval(function () {
if (i > 3000) {
tmp = parseInt(tmp * 0.99);
if (tmp > m) {
tmp = m;
clearInterval(timer);
msg(m);
}
run(tmp);
}
else if (i > 1000) {
i = i + 45;
run(i);
}
else {
i = parseInt((i + 1) * 1.01);
run(i);
}
}, 50);
}
return { rotate: rotate }
} ();
function showMsg() {
mRotate.rotate("demo", function msg(m) {
if (m > -90 && m < -30) {
m$("msg").innerHTML += "22222222";
}
else if (m > -150 && m < -90) {
m$("msg").innerHTML += "333333333";
}
else if (m > -210 && m < -150) {
m$("msg").innerHTML += "444444";
}
else if (m > -270 && m < -210) {
m$("msg").innerHTML += "5555555";
}
else if (m > -330 && m < -270) {
m$("msg").innerHTML += "6666666";
} else {
m$("msg").innerHTML += "111111111";
}
m$('restart').style.display = "block";
});
}
window.onload = function () {
m$('test').onclick = function () {
m$('test').style.display = "none";
showMsg();
}
m$('restart').onclick = function () {
m$('restart').style.display = "none";
if (isIE) {
m$("demo").style.top = "0px";
m$("demo").style.left = "0px";
} else if (m$("demo").style.MozTransform !== undefined) {
m$("demo").style.MozTransform = 'rotate(0deg)';
} else if (m$("demo").style.OTransform !== undefined) {
m$("demo").style.OTransform = 'rotate(0deg)';
} else if (m$("demo").style.webkitTransform !== undefined) {
m$("demo").style.webkitTransform = 'rotate(0deg)';
} else {
m$("demo").style.transform = 'rotate(0deg)';
}
m$('test').style.display = "block";
i = 0;
}
}
</script>
</body>
</html>