js九宫格抽奖 原生JS实现九宫格抽奖

<div class="wrapper">
    <div>谢谢惠顾</div>
    <div>十万元现金</div>
    <div>谢谢惠顾</div>
    <div>iphone11</div>
    <div>抽奖</div>
    <div>美的冰箱</div>
    <div>谢谢惠顾</div>
    <div>50元红包</div>
    <div>谢谢惠顾</div>
  </div>
<div class="result"></div>

<style>
    .wrapper {
      width: 300px;
      height: 300px;
      display: flex;
      flex-flow: row wrap;
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      bottom: 0;
      margin: auto;
      border: 1px solid red;
    }
    
    .wrapper div {
      flex: none;
      width: 100px;
      height: 100px;
      box-sizing: border-box;
      border: 1px solid red;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    
    .active {
      background-color: red;
    }
    
    .wrapper div:nth-child(5) {
      cursor: pointer;
    }
    
    .result {
      height: 100px;
      display: inline-block;
      position: absolute;
      top: 50px;
      left: 0;
      right: 0;
      margin: auto;
      text-align: center;
      line-height: 100px;
      font-size: 40px;
      font-weight: 700;
      color: #ff4400;
    }
</style>

<script>
    var t, m, num, time, index, target, current;
    //以索引值为0，1，2，5，8，7，6，3的div元素为循环目标，
    //因为以num总数递减的方式进行循环，故将数组倒序定义
    var arr = [3, 6, 7, 8, 5, 2, 1, 0];
    var div = document.querySelectorAll('.wrapper div');
    var result = document.querySelector('.result');
    div[4].onclick = function() {
      clearInterval(time);
      div[4].innerHTML = '抽奖中...';
      result.innerHTML = '';
      //中奖目标设为0到7的随机整数
      target = Math.floor(Math.random() * 8);
      //起始位置设为随机，且以num为总的循环数
      num = Math.floor(Math.random() * 8) + 40;
      //将总循环数的2/3保存，方便调整速率峰值出现的时间
      //若m为总循环的1/2，则速度峰值会在总时长的中间出现
      m = Math.floor(num * 2 / 3);
      //此处if语句可限制中奖，从第一个开始外圈顺时针分别对应7，6，5，4，3，2，1，0
      //如设置target == 6 即限制中十万元现金，以下代码为100%不中奖
      if (target == 6|| target == 4 || target == 2 || target == 0) { 
         target++;
       }
      speed();

      function speed() {
        //将循环目标div的索引值转换为循环总数的表达式
        index = arr[num % 8];
        //给当前循环元素添加样式，并移除之前的样式
        if (current) {
          current.remove('active');
        }
        div[index].classList.add('active');
        current = div[index].classList;
        //速度函数，可调试速率
        t = Math.floor(Math.pow((num - m), 2) + 250);
        //一次性定时器，嵌套递归循环控制速度
        time = setTimeout(function() {
            speed()
          }, t)
        //判断中奖结果
        if (num == target) {
          clearTimeout(time);
          div[4].innerHTML = '抽奖';
          switch (target) {
            case 6:
              result.innerHTML = '恭喜您抽中' + div[arr[target % 8]].innerHTML + '大奖';
              break;
            case 4:
              result.innerHTML = '恭喜您抽中' + div[arr[target % 8]].innerHTML;
              break;
            case 2:
              result.innerHTML = '恭喜您抽中' + div[arr[target % 8]].innerHTML;
              break;
            case 0:
              result.innerHTML = '恭喜您抽中' + div[arr[target % 8]].innerHTML;
              break;
            default:
              result.innerHTML = div[arr[target % 8]].innerHTML;
          }
        }
        num--;
      }
    }


</script>