写在开头
上期代码主要实现PC端电商网站商品放大效果，本期就来实现积分随机抽奖效果，开发久了很多功能都是通过框架组件库来完成，但是如果组件满足不了开发需求，还需要开发人员手动封装组件，专门出这样一期文章，通过原生js实现一些特定功能，功能也比较简单，也是想借助这样一个简单的功能，然后来帮助大家了解我们JavaScript，在前端中的作用，另外也培养下我们的代码思维，那我们本次就通过由简单到复杂循序渐进，这份专栏中我们会带领大家用前端实现拼图、无缝轮播图、图片瀑布流、读心术小游戏等等有趣的小功能，纯前端语言实现，都会陆续带给大家。
功能介绍
转盘抽奖功能，正常开发中中奖概率，抽奖次数都是后台数据返回的，就像你拼西西抽红包，因为是纯前端完成，概率完全随机数，页面逻辑代码中注释很完善，请看下图代码
页面创建
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>随机抽奖</title><link rel="stylesheet" href="demo.css">
</head>
<body><!-- 整体 --><div class="main"><!-- 抽奖区域 --><div class="content-container"><!-- 抽奖项 --><div class="price-list"><img src="../img/prize_1.png" alt=""><span>IphoneX19</span></div><div class="price-list"><img src="../img/prize_2.png" alt=""><span>金币20个</span></div><div class="price-list"><img src="../img/prize_3.png" alt=""><span>华为Mate 90 一部</span></div><div class="price-list"><img src="../img/prize_4.png" alt=""><span>金币10个</span></div><div class="price-list"><img src="../img/prize_5.png" alt=""><span>谢谢参与</span></div><div class="price-list"><img src="../img/prize_6.png" alt=""><span>手机优惠券</span></div><div class="price-list"><img src="../img/prize_7.png" alt=""><span>电脑优惠券</span></div><div class="price-list"><img src="../img/prize_8.png" alt=""><span>U盘</span></div><!-- 中间区域 --><div class="hander-container"><div class="inner-container"><img src="../img/center_1.png" alt="" class="hander-left"><div class="hander-container-middle">还可以抽奖 <span class="price-number">0</span>次</div><div class="hander-container-btn"></div></div></div></div><!-- 弹窗区域 --><div class="dialog-container"><div class="dialog-main"><div class="head"><span class="title">温馨提示</span><span class="close">×</span></div><div class="content">每次抽奖将消耗 8000 积分</div><div class="dialog-main-footer"><div class="button">再来一次</div></div></div></div></div><script src="./demo.js"></script>
</body>
</html>
样式搭建
* {margin: 0;padding: 0;
}
/* 大背景 */
.main {height: 546px;background-image: url('../img/banner-bg.jpg');position: relative;
}
/* 抽奖背景 */
.content-container {position: absolute;width: 874px;height: 458px;background-image: url('../img/bg.png');/* 水平垂直居中 */left: 50%;top: 50%;transform: translate(-50%,-50%);
}
/* 奖项区域 */
.price-list {width: 270px;height: 100px;position: absolute;padding: 5px;text-align: center;background-color: #622230;border: 1px solid #722536;border-radius: 5px;box-sizing: border-box;
}.price-list>img {max-height: 75px;position: absolute;left: 30px;top: 15px;
}.price-list>span {font-size: 19px;color: #ffb100;font-weight: bold;position: absolute;left: 102px;top: 36px;width: 164px;
}.price-list:nth-child(1) {top: 22px;left: 26px;
}.price-list:nth-child(2) {top: 22px;left: 302px;
}.price-list:nth-child(3) {top: 22px;right: 26px;
}.price-list:nth-child(4) {top: 129px;right: 26px;width: 100px;height: 200px;
}.price-list:nth-child(4)>img,
.price-list:nth-child(8)>img {position: absolute;left: 50%;transform: translateX(-50%);top: 15px;
}.price-list:nth-child(4)>span,
.price-list:nth-child(8)>span {position: absolute;left: 50%;transform: translateX(-50%);bottom: 36px;top: auto;
}.price-list:nth-child(5) {bottom: 22px;right: 26px;
}.price-list:nth-child(6) {bottom: 22px;left: 302px;
}.price-list:nth-child(7) {bottom: 22px;left: 26px;
}.price-list:nth-child(8) {top: 129px;left: 26px;width: 100px;height: 200px;
}/* 中间抽奖区域 */
.hander-container {width: 614px;height: 198px;background-image: url('../img/middle-bg.png');position: absolute;left: 50%;top: 50%;transform: translate(-50%,-50%);
}.inner-container {display: table-cell;vertical-align: middle;padding: 0 20px;padding: 50px;
}.hander-left {float: left;vertical-align: middle;
}.hander-container-middle {float: left;color: #ffd200;font-size: 30px;font-weight: bold;margin: 17px 0 0 18px;
}.hander-container-btn {width: 210px;height: 102px;background-image: url('../img/btn.png');float: right;cursor: pointer;
}.active {background-color: #ffd100;
}.active>span {color: #470c1b;
}/* 对话框样式 */.dialog-container {position: fixed;width: 100%;height: 100%;left: 0;top: 0;background-color: rgba(0, 0, 0, .5);display: none;
}.dialog-main {width: 400px;background-color: #fff;position: absolute;left: 50%;top: 30%;transform: translate(-50%, -50%);box-sizing: border-box;
}.dialog-main>.head {height: 50px;line-height: 50px;background-color: #e99c3d;border-bottom: 1px solid #ddd;box-sizing: border-box;padding: 0 20px;
}.dialog-main>.head>.title {float: left;color: #fff;font-size: 18px;
}.dialog-main>.head>.close {float: right;color: #fff;font-size: 42px;cursor: pointer;
}.dialog-main-footer {text-align: right;margin: 20px;
}.dialog-main>.content {text-align: center;margin: 20px;color: #622230;font-weight: bold;font-size: 20px;
}.dialog-main-footer>.button {background-color: #fca825;height: 28px;cursor: pointer;display: inline-block;line-height: 28px;color: #fff;padding: 0 10px;border-radius: 3px;
}
主要逻辑
/*
1: 定义抽奖次数渲染1-1 获取DOM元素1-2 定义剩余的抽奖次数
2: 点击抽奖按钮,实现滚动抽奖效果(复杂度高)2-1 获取点击按钮 ,绑定点击事件2-2 为每一个list选项添加类名,实现高亮状态2-3 定义当前高亮的列表项索引值2-4 使用定时器实现滚动效果2-5 使用随机数定义停止条件
3: 弹窗处理 3-1 打开弹窗.显示中奖信息(处理未中奖时的弹窗提示内容)3-2 打开弹窗的同时,减少剩余的抽奖次数3-3 关闭按钮的事件绑定3-4 再来一次按钮事件绑定
4: 定义runGame函数
5: timer定时器bug修复*/
(function(){// 开始抽奖按钮var startBtn = document.querySelector('.hander-container-btn')// 奖项var priceList =document.querySelectorAll('.price-list')// 弹窗区域var dialogContainer = document.querySelector('.dialog-container')// 弹窗内容区域var priceContent = document.querySelector('.dialog-container .content')var index = -1var timer = nullvar number = 5var currentIndex = null// 弹窗关闭按钮var closeBtn = document.querySelector('.close')// 弹窗按钮再来一次var confirmBtn = document.querySelector('.dialog-main-footer .button')// 剩余抽奖次数var priceNumber = document.querySelector('.price-number')// 初始化var init = function(){priceNumber.innerHTML = numberinitEvent()}// 初始化函数var initEvent = function(){// 添加监听事件startBtn.addEventListener('click',onStartBtnClick)closeBtn.addEventListener('click',onCloseBtnClick)confirmBtn.addEventListener('click',onConfirmBtnClick)}// 开始抽奖var onStartBtnClick = function(){if(timer) returnindex = -1if(number === 0) returnrunGame()}// 转盘转动var runGame = function(){// 获取随机数var ranDom = Math.floor(Math.random() * 6000 + 3000)timer = setInterval(function(){ranDom -= 200if(ranDom < 200){// 小于200停止转盘clearInterval(timer)timer = null// 打开弹窗openDialog()return}currentIndex = ++index % priceList.lengthpriceList.forEach(function(el){// 先移除背景滚动效果el.classList.remove('active')})// 给滚动项加上背景高亮背景priceList[currentIndex].classList.add('active')},60)}// 打开弹窗var openDialog = function(){priceNumber.innerHTML = --numberif(number === 0){document.querySelector('.dialog-main-footer .button').innerHTML = '确定'}dialogContainer.style.display = 'block'var spanText = document.querySelector('.active span').innerHTMLif(spanText.includes('谢谢参与')){priceContent.innerHTML = '很遗憾您没有中奖'}else {priceContent.innerHTML = '恭喜您获得' + spanText}}// 关闭弹窗var onCloseBtnClick = function(){dialogContainer.style.display = 'none'}// 弹窗确认按钮 && 再来一次var onConfirmBtnClick = function(){index = -1dialogContainer.style.display = 'none'if(number === 0 || timer) returnrunGame()}init()
})()
结尾总结
点击抽奖按钮之后，里面涉及的功能有些许复杂，需要一步步捋下来，遇到问题就一步步解决，给一个参考图
