为了获取客户、回馈客户，平台一般会推出抽奖活动类的营销页。因此web页面中，有各式各样的抽奖效果。
格子式(九宫格)，背景滚动式(数字/文字/图案)，旋转式(转盘)，游戏式(砸蛋/拼图...)......
这里来讲解下转盘抽奖效果。
当用户进入这个抽奖页面时，一般会“华丽”的设计所吸引，虽然明知中奖几率几乎等于0，图个运气，都会去点“开始抽奖”，于是“折腾”开始了。
你还没有登录，请登录后再来
你还没有抽奖资格，请做做“什么”后再来
你的抽奖机会用完了，请明天再来
很抱歉，你没有中奖
。。。
来看下效果：
在BKY预览效果无语了，弹出插件都不弹出了。
实际是这样的：
贴上代码，仅供参考：
页面代码:
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no"/>
<title>旋转-转盘-抽奖</title>
<style type="text/css">
*{margin: 0; padding: 0;}
#ww_page{ overflow:hidden; 100%;}
#ww_rotate{position: relative; margin: 0 auto; 640px; height:640px; }
#ww_plate{position:absolute; top:0; left:0;640px; height:640px; background:url(http://i13.tietuku.com/416f769edc909de0.png) center no-repeat;background-size: 100% 100%; transition: none;}
#ww_arrow{position:absolute; top:205px; left:50%; z-index: 10;margin-left: -75px;150px;height:190px; background:url(http://i13.tietuku.com/0e0b1c875d346f4d.png) center no-repeat; }
</style>
</head>
<body>
<div id="ww_page">
<div id="ww_box">
<div id="ww_rotate">
<div id="ww_plate"></div>
<div id="ww_arrow"></div>
</div>
</div>
</div>
<link rel="stylesheet" type="text/css" href="js/Tips/mTips.css" />
<script type="text/javascript" src="js/Tips/mTips.min.js"></script>
<script type="text/javascript" src="js/utils.js"></script>
<script type="text/javascript" src="mRotate.js"></script>
<script type="text/javascript">
//缩放
scalePage('#ww_box');
// 奖品数据
var prizeData = [
{
id: 1,
prize: "一等奖",
angle: 3600
}, {
id: 2,
prize: "二等奖",
angle: 3720
}, {
id: 3,
prize: "三等奖",
angle: 3840
}, {
id: 4,
prize: "再接再厉",
angle: 3750
}, {
id: 5,
prize: "要加油哦",
angle: 3865
}, {
id: 6,
prize: "谢谢参与",
angle: 3930
}
];
//旋转
var arrow = document.getElementById('ww_arrow'),
plate = document.getElementById('ww_plate'),
isRotate = false;
arrow.onclick = function() {
if (isRotate) return;
isRotate = true;
var num = (Math.random() * prizeData.length) >> 0,
data = prizeData[num];
// console.log(num);
// console.time('计时');
new Rotate({
el: plate,
//angle: 90,
animateTo: data.angle,
duration: 5000,
easeing: 'easeInOutCirc',
end: function() {
// console.timeEnd('计时');
isRotate = false;
Tips.alert(data.prize);
}
});
};
</script>
</body>
</html>
旋转主程序mRotate.js
/**
* LBS Rotate
* Date: 2014-12-20
* ==================================
* opts.el 旋转对象(一个字符串的CSS选择器或者元素对象)
* opts.angle 初始角度 默认0
* opts.animateTo 目标角度
* opts.duration 持续时间 默认1000(毫秒)
* opts.easing 动画效果 (easeOutSine默认 easeInOutSine easeInOutCirc)
* opts.end 旋转完成 执行函数
* ==================================
**/
var Rotate = function(opts) {
opts = opts || {};
if (typeof opts.el === undefined) return;
this.el = typeof opts.el === 'string' ? document.querySelector(opts.el) : opts.el;
this.angle = opts.angle || 0;
this.animateTo = opts.animateTo || this.angle + 360;
this.duration = opts.duration || 1000;
this.easing = (opts.easing && this.tween[opts.easing]) || this.tween.easeOutSine;
this.end = opts.end || function() {};
this.animated = false;
this.init();
};
Rotate.prototype = {
init: function() {
this.rotate(this.angle);
this.start();
},
start: function() {
this.animate();
},
animate: function() {
if (this.animated) return;
var start = this.angle,
end = this.animateTo,
change = end - start,
duration = this.duration,
startTime = +new Date(),
ease = this.easing,
_this = this;
if (start == end) {
this.end && this.end();
return;
}
this.animated = true;
! function animate() {
var nowTime = +new Date(),
timestamp = nowTime - startTime,
delta = ease(timestamp / duration);
_this.rotate(start + delta * change);
if (duration <= timestamp) {
_this.rotate(end);
_this.animated = false;
_this.end && _this.end();
} else {
setTimeout(animate, 17);
}
}();
},
rotate: function(angle) {
this.setTransform(angle % 360);
},
setTransform: function(v) {
v = v || 0;
this.setStyle(this.el, 'transform', 'rotate(' + v + 'deg)');
},
setStyle: function(el, p, v) {
!this.cache && (this.cache = {});
!this.cache[el] && (this.cache[el] = {});
!this.cache[el][p] && (this.cache[el][p] = this.prefix(p));
el.style[this.cache[el][p] || this.prefix(p)] = v;
},
prefix: function(p) {
var style = document.createElement('div').style;
if (p in style) return p;
var prefix = ['webkit', 'Moz', 'ms', 'O'],
i = 0,
l = prefix.length,
s = '';
for (; i < l; i++) {
s = prefix[i] + '-' + p;
s = s.replace(/-D/g, function(match) {
return match.charAt(1).toUpperCase();
});
if (s in style) return s;
}
},
tween: {
easeOutSine: function(pos) {
return Math.sin(pos * (Math.PI / 2));
},
easeInOutSine: function(pos) {
return (-.5 * (Math.cos(Math.PI * pos) - 1));
},
easeInOutCirc: function(pos) {
if ((pos /= 0.5) < 1) return -0.5 * (Math.sqrt(1 - pos * pos) - 1);
return 0.5 * (Math.sqrt(1 - (pos -= 2) * pos) + 1);
}
}
};
很简单的代码，就是一个动画函数，改变元素的旋转rotate属性。
CSS3 transform 属性：http://www.w3school.com.cn/cssref/pr_transform.asp
动画函数如下，获得元素的初始角度(起点)，目标角度(终点)，要多久(持续的时间)，动画效果(缓动公式)
animate: function() {
if (this.animated) return;
var start = this.angle, //起点
end = this.animateTo, //目的地
change = end - start, //距离
duration = this.duration, //持续时间
startTime = +new Date(),
ease = this.easing, //运动效果
_this = this;
if (start == end) {
this.end && this.end();
return;
}
this.animated = true;
!function animate() {
var nowTime = +new Date(),
timestamp = nowTime - startTime,
delta = ease(timestamp / duration);
_this.rotate(start + delta * change);
if (duration <= timestamp) {
_this.rotate(end);
_this.animated = false;
_this.end && _this.end();
} else {
setTimeout(animate, 17);
}
}();
}
设置旋转属性
rotate: function(angle) {
this.setTransform(angle % 360);
},
setTransform: function(v) {
v = v || 0;
this.setStyle(this.el, 'transform', 'rotate(' + v + 'deg)');
},
setStyle: function(el, p, v) {
!this.cache && (this.cache = {});
!this.cache[el] && (this.cache[el] = {});
!this.cache[el][p] && (this.cache[el][p] = this.prefix(p));
el.style[this.cache[el][p] || this.prefix(p)] = v;
},
prefix: function(p) {
var style = document.createElement('div').style;
if (p in style) return p;
var prefix = ['webkit', 'Moz', 'ms', 'O'],
i = 0,
l = prefix.length,
s = '';
for (; i < l; i++) {
s = prefix[i] + '-' + p;
s = s.replace(/-D/g, function(match) {
return match.charAt(1).toUpperCase();
});
if (s in style) return s;
}
}
实际抽奖流程：点击抽奖按钮，发送ajax，得到一个结果数据，执行抽奖程序，显示结果。
了解动画函数，结合缓动公式，是做出各种炫酷的效果的基础。