中奖几率基本不写在js里，因为js可以被破解和修改，都是写在后端的。
5分给你个程序。。。自己参考改吧
<input type="button" value="开始旋转" onclick="spin()" style="float: left" />
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<canvas id="wheelcanvas" width="500" height="500"></canvas>
<script type="application/javascript">
var colors = ["#B8D430", "#3AB745", "#029990", "#3501CB",
"#2E2C75", "#673A7E", "#CC0071", "#F80120",
"#F35B20", "#FB9A00", "#FFCC00", "#FEF200"]
var restaraunts = ["北京", "上海", "天津", "南京",
"杭州", "深圳", "武汉", "济南",
"重庆", "大连", "合肥", "郑洲"]
var startAngle = 0
var arc = Math.PI / 6
var spinTimeout = null
var spinArcStart = 10
var spinTime = 0
var spinTimeTotal = 0
var ctx
function draw() {
drawRouletteWheel()
}
function drawRouletteWheel() {
var canvas = document.getElementById("wheelcanvas")
if (canvas.getContext) {
var outsideRadius = 200
var textRadius = 160
var insideRadius = 125
ctx = canvas.getContext("2d")
ctx.clearRect(0,0,500,500)
ctx.strokeStyle = "black"
ctx.lineWidth = 2
ctx.font = 'bold 12px sans-serif'
for(var i = 0i <12i++) {
var angle = startAngle + i * arc
ctx.fillStyle = colors[i]
ctx.beginPath()
ctx.arc(250, 250, outsideRadius, angle, angle + arc, false)
ctx.arc(250, 250, insideRadius, angle + arc, angle, true)
ctx.stroke()
ctx.fill()
ctx.save()
ctx.shadowOffsetX = -1
ctx.shadowOffsetY = -1
ctx.shadowBlur= 0
ctx.shadowColor = "rgb(220,220,220)"
ctx.fillStyle = "black"
ctx.translate(250 + Math.cos(angle + arc / 2) * textRadius, 250 + Math.sin(angle + arc / 2) * textRadius)
ctx.rotate(angle + arc / 2 + Math.PI / 2)
var text = restaraunts[i]
ctx.fillText(text, -ctx.measureText(text).width / 2, 0)
ctx.restore()
}
//Arrow
ctx.fillStyle = "black"
ctx.beginPath()
ctx.moveTo(250 - 4, 250 - (outsideRadius + 5))
ctx.lineTo(250 + 4, 250 - (outsideRadius + 5))
ctx.lineTo(250 + 4, 250 - (outsideRadius - 5))
ctx.lineTo(250 + 9, 250 - (outsideRadius - 5))
ctx.lineTo(250 + 0, 250 - (outsideRadius - 13))
ctx.lineTo(250 - 9, 250 - (outsideRadius - 5))
ctx.lineTo(250 - 4, 250 - (outsideRadius - 5))
ctx.lineTo(250 - 4, 250 - (outsideRadius + 5))
ctx.fill()
}
}
function spin() {
spinAngleStart = Math.random() * 10 + 10
spinTime = 0
spinTimeTotal = Math.random() * 3 + 4 * 1000
rotateWheel()
}
function rotateWheel() {
spinTime += 30
if(spinTime >= spinTimeTotal) {
stopRotateWheel()
return
}
var spinAngle = spinAngleStart - easeOut(spinTime, 0, spinAngleStart, spinTimeTotal)
startAngle += (spinAngle * Math.PI / 180)
drawRouletteWheel()
spinTimeout = setTimeout('rotateWheel()', 30)
}
function stopRotateWheel() {
clearTimeout(spinTimeout)
var degrees = startAngle * 180 / Math.PI + 90
var arcd = arc * 180 / Math.PI
var index = Math.floor((360 - degrees % 360) / arcd)
ctx.save()
ctx.font = 'bold 30px sans-serif'
var text = restaraunts[index]
ctx.fillText(text, 250 - ctx.measureText(text).width / 2, 250 + 10)
ctx.restore()
}
function easeOut(t, b, c, d) {
var ts = (t/=d)*t
var tc = ts*t
return b+c*(tc + -3*ts + 3*t)
}
draw()
</script>
本文实例为大家分享了js抽奖程序的编写代码，以及编写注意事项，感兴趣的小伙伴们可以参考一下
代码：
<!DOCTYPE
html>
<html
lang="en">
<head>
<meta
charset="UTF-8">
<title>简单抽奖（可用键盘）</title>
<style>
*{margin:0padding:0}
.box{width:
400pxheight:
300pxmargin:50px
autobackground:
red}
.title{color:
#ffffont-size:
30pxfont-weight:700pxpadding:
50px
0text-align:
centerheight:40px}
.btm{text-align:
centerpadding:20px
0}
.btm
a{display:
inline-blockwidth:
120pxheight:60pxline-height:
60pxbackground:
#FEF097margin:0
10pxtext-decoration:
none}
</style>
<script>
var
data=['Iphone','Ipad','笔记本','相机','谢谢参与','充值卡','购物券'],
timer=null,//定时器
flag=0//阻止多次回车
window.onload=function(){
var
play=document.getElementById('play'),
stop=document.getElementById('stop')
//
开始抽奖
play.onclick=playFun
stop.onclick=stopFun
//
键盘事件
document.onkeyup=function(event){
event
=
event
||
window.event
//
回车键的code值：13
if(event.keyCode==13){
if(flag==0){
playFun()
flag=1
}else{
stopFun()
flag=0
}
}
}
function
playFun(){
var
title=document.getElementById('title')
var
play=document.getElementById('play')
clearInterval(timer)
timer=setInterval(function(){
var
random=Math.floor(Math.random()*data.length)
title.innerHTML=data[random]
},60)
play.style.background='#999'
}
function
stopFun(){
clearInterval(timer)
var
play=document.getElementById('play')
play.style.background='#FEF097'
}
}
</script>
</head>
<body>
<div
class="box">
<div
class="title"
id="title">淘家趣抽奖</div>
<div
class="btm">
<a
href="javascript:"
id="play">开始</a>
<a
href="javascript:"
id="stop">停止</a>
</div>
</div>
</body>
</html>
注意点：
1.随机数，取数组的其中一个；取0-n之间：Math.random()*(n+1)
2.定时器，开始抽奖时要停止前面的一次抽奖，不然会定时器重叠
3.按键 *** 作，要判断是抽奖进行中，还是未开始，所有设置了变量
flag
想要学习更多关于javascript抽奖功能，请参考此专题：javascript实现抽奖功能
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。
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