/**
動畫結(jié)束事件兼容
**/
whichTransitionEvent(){
 let el = document.createElement('span'),
 transitions = {
 'transition':'transitionend',
 'OTransition':'oTransitionEnd',
 'MozTransition':'transitionend',
 'WebkitTransition':'webkitTransitionEnd'
 };
 for(let t in transitions){
 if( el.style[t] !== undefined ){
  return transitions[t];
 }
 }
 el = null;
}

<template>
 <div>
 <h3>轉(zhuǎn)盤抽獎</h3>
 <div class="round_box" >
  <img class="img_rotate" ref="rotImg" src="../assets/zhuan.png" alt="">
  <div class="center">
  <div class="pointer" ></div>
  </div>
 </div>
 <button @click="toDraw" >點擊抽獎</button>
 </div>
</template>

<script>
export default {
 name:'rotaryDraw',
 data() {
 return {
  rotate: 0,
  resetRotate: 0,
  hitId: 1,// 1-10
  drawStatus: false
 }
 },
 async mounted() {
 await this.$nextTick();
 let evenTransition = this.whichTransitionEvent();
 let img = this.$refs.rotImg;
 let that = this;
 const hitAre = [ '30M流量包','20金幣','20M流量包','10M流量包','5金幣',
    '謝謝參與','10金幣','50M流量包','2金幣','100M流量包'
   ];
 // 監(jiān)聽 動畫結(jié)束 
 img.addEventListener(evenTransition,tranHand,false);

 function tranHand() {
  // 復(fù)位
  that.resetRotate = that.rotate > 360 ? that.rotate % 360 : 0;
  img.style.transition = "none 0s ease 0s";
  img.style.transform = `rotate(${that.resetRotate}deg)`; 
  alert(`抽獎結(jié)果【 ${hitAre[that.hitId - 1]} 】`);
  that.drawStatus = false
 }
 },
 methods: {
 start() {
  this.$refs.rotImg.style.transition = "all 3s ease 0s";
  this.$refs.rotImg.style.transform = `rotate(${this.rotate}deg)`;
 },
 toDraw() {
  if(this.drawStatus){
  console.log('正在抽獎中');
  return
  }
  // 標(biāo)記狀態(tài)
  this.drawStatus = true
  /**
  * 圓盤共 10 份 每份 36度, 停位置(id)度數(shù) (id - 1)*36 
  * 基數(shù) 3圈 360*4
  * this.rotate 當(dāng)前角度
  * **/ 
  let reset = 360 * 4;
  let idx = this.getRandomInt(1,11);
  // 設(shè)置命中
  this.hitId = idx;
  // 需要多轉(zhuǎn)角度
  let addRotate = this.resetRotate > 0 ? 360 - this.resetRotate : 0;
  // 總共角度
  let allRotate = this.rotate + (idx - 1) * 36 + reset + addRotate;
  // 角度限制
  this.rotate = this.setRotate(allRotate);

  this.start()
 },
 // 遞歸計算角度 不超過 360*6
 setRotate(deg) {
  let rest = deg - 360;
  return rest > 360*6 ? this.setRotate(rest) : deg;
 },
 getRandomInt(min, max) {
  // 向上收
  min = Math.ceil(min);
  // 向下收
  max = Math.floor(max);
  return Math.floor(Math.random() * (max - min)) + min; //不含最大值，含最小值
 },
 // 動畫兼容
 whichTransitionEvent(){
  let el = document.createElement('span'),
  transitions = {
  'transition':'transitionend',
  'OTransition':'oTransitionEnd',
  'MozTransition':'transitionend',
  'WebkitTransition':'webkitTransitionEnd'
  };
  for(let t in transitions){
  if( el.style[t] !== undefined ){
   return transitions[t];
  }
  }
  el = null;
 }
 }

}
</script>

<style lang="scss" >
.img_rotate{
 transform: rotate(0deg);
}
.round_box{
 width: 100%;
 max-width: 375px;
 position: relative;
 overflow: hidden;
 img{
 width: 100%;
 }
 .center{
 position: absolute;
 top: 50%;
 left: 50%;
 transform: translate(-50%,-50%);
 .pointer{
  width: 5px;
  height: 90px;
  background-color: #f40;
  position: absolute;
  top: -90px;
 }
 .pointer::before{
  content:'';
  width: 0;
  height: 0;
  border-top: 15px solid transparent;
  border-right: 15px solid transparent;
  border-bottom: 15px solid #f40;
  border-left: 15px solid transparent;
  position: absolute;
  top: -20px;
  left: 50%;
  transform: translateX(-50%);
 }
 }
}

</style>

/**
比如：
基數(shù)3圈 reset 360*3
停留位置 第二個 （2 - 1）* 36 = 36
總共角度 360*3 + 36
動畫停止后，因為還要繼續(xù)旋轉(zhuǎn)，所以不可能把角度一直增加，因此需要復(fù)位 
360*3 + 36 其實可以考慮 就轉(zhuǎn)了 36度，然后再增加需要轉(zhuǎn)的角度
**/