九宫格转圈圈抽奖活动，有加速，减速效果

在线访问demo和代码在底部

代码，复制就可以跑

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>🐯🐯🐯</title><style>* {margin: 0;padding: 0;}.box {position: relative;width: 300px;height: 300px;border: 1px solid grey;}.item {width: 80px;height: 80px;position: absolute;background-color: gainsboro;display: flex;justify-content: center;align-items: center;}.item.active {background-color: red;font-weight: 600;}</style>
</head><body><h1 id="result">这一次结果</h1><div class="box" id="box"></div><button id="start">开始</button><script>let box = document.querySelector("#box")let start = document.querySelector("#start")let result = document.querySelector("#result");//奖项个数const itemLen = 8;let arr = [];//开启位置let startIndex = 0;let timer = null;let speed = 80;//随机工具函数function getRandomNumber(min, max) {return Math.floor(Math.random() * (max - min + 1)) + min;}//基础圈数let baseTarget = getRandomNumber(4, 6) * itemLen;//开奖索引let targetIndex = null;//基础圈数+开奖索引let totalCount = 0;//初始化dom渲染for (let i = 0; i < itemLen; i++) {arr.push("奖项：" + i)}let domStr = document.createDocumentFragment();const domItems = []for (let i = 0; i < arr.length; i++) {let dom = document.createElement("div");dom.className = "item";dom.innerHTML = arr[i];switch (i) {case 0:dom.style.top = 0;dom.style.left = 0;break;case 1:dom.style.top = 0;dom.style.left = "110px";break;case 2:dom.style.top = 0;dom.style.right = 0;break;case 3:dom.style.top = "100px";dom.style.right = 0;break;case 4:dom.style.bottom = 0;dom.style.right = 0;break;case 5:dom.style.bottom = 0;dom.style.right = "110px";break;case 6:dom.style.bottom = 0;dom.style.left = 0;break;case 6:dom.style.bottom = "100px";dom.style.left = 0;break;case 7:dom.style.bottom = "120px";dom.style.left = 0;break;}box.appendChild(dom)domItems.push(dom);}box.appendChild(domStr);function frame() {//清除定时器clearTimeout(timer);//获取递增过程的索引变量对饮奖项的索引let currentpos = startIndex % itemLen;//更新奖项的高亮样式for (let i = 0; i < itemLen; i++) {if (currentpos == i) {domItems[i].classList.add("active");}else {domItems[i].classList.remove("active");}}//如果达到中奖的目标位置就停止if (startIndex == totalCount) {clearTimeout(timer);return;}//地址的索引不断的递增startIndex++;//获取运行比例let percent = Math.floor(startIndex / totalCount * 100);//递增的索引跑了目标值的50%前都加快if (percent <= 50) {//需要兜底，否则会出意外if (speed > 10) {speed--;}}else {//后50%速度开始减速speed += 6;}//这里的定时器的时间是动态的！！！！重要timer = setTimeout(() => {frame();}, speed)}function startGame() {//基础圈数baseTarget = getRandomNumber(4, 6) * itemLen;//随机目标位置targetIndex = getRandomNumber(0, 7);//总个数totalCount = baseTarget + targetIndex;result.innerHTML = "这次开奖的结果：" + arr[targetIndex];startIndex = 0;//初始化速度speed = 80;//重置完所有配置后，开始跑定时器frame();}start.onclick = startGame;</script>
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