转盘抽奖功能(附加代码)

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">&times;</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 = -1
    var timer = null
    var number = 5
    var 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 = number
        initEvent()
    }
    // 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) return
        index = -1
        if(number === 0) return
        runGame()
    }
    // 转盘转动
    var runGame = function(){
        // 获取随机数
        var ranDom = Math.floor(Math.random() * 6000 + 3000)
        timer = setInterval(function(){
            ranDom -= 200
            if(ranDom < 200){
                // 小于200停止转盘
                clearInterval(timer)
                timer = null
                // 打开弹窗
                openDialog()
                return
            }
            currentIndex = ++index % priceList.length
            priceList.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 = --number
        if(number === 0){
            document.querySelector('.dialog-main-footer .button').innerHTML = '确定'

        }
        dialogContainer.style.display = 'block'
        var spanText = document.querySelector('.active span').innerHTML
        if(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 = -1
        dialogContainer.style.display = 'none'
        if(number === 0 || timer) return
        runGame()
    }

    init()
})()