vue 动画 雪花下落 消失 再显示 代码

好的，下面是Vue动画实现雪花下落消失再显示的代码：

<template>
  <div class="snow-container">
    <transition-group
      :css="false"
      name="snow"
      mode="out-in"
      @before-enter="beforeEnter"
      @after-enter="afterEnter"
      @before-leave="beforeLeave"
      @after-leave="afterLeave"
    >
      <div
        v-for="(snow, index) in snowList"
        :key="snow.id"
        class="snow"
        :style="{ top: snow.y + 'px', left: snow.x + 'px' }"
      />
    </transition-group>
  </div>
</template>

<script>
const MAX_SNOW_NUM = 20;
const SNOW_SIZE = 10;

export default {
  name: 'snow-fall',
  data() {
    return {
      snowList: [] // 雪花列表
    };
  },
  methods: {
    // 生成一个随机的雪花实例
    createSnow() {
      const id = Date.now + Math.round(Math.random() * 100);
      const x = Math.round(Math.random() * window.innerWidth);
      const y = Math.round(Math.random() * -500);
      return { id, x, y };
    },
    // 添加雪花
    addSnow() {
      if (this.snowList.length >= MAX_SNOW_NUM) return;
      const snow = this.createSnow();
      this.snowList.push(snow);
    },
    // 雪花进入前的动画
    beforeEnter(el) {
      const delay = Math.round(Math.random() * 2000);
      el.style.transitionDelay = delay + 'ms';
      el.style.opacity = 0;
    },
    // 雪花进入后的动画
    afterEnter(el) {
      el.style.transitionDelay = 0;
      const snow = this.snowList.find(s => s.id === el.key);
      snow.y = window.innerHeight;
      this.$forceUpdate(); // 强制更新Dom
    },
    // 雪花离开前的动画
    beforeLeave(el) {
      el.style.opacity = 0;
    },
    // 雪花离开后的动画
    afterLeave(el) {
      const snowIndex = this.snowList.findIndex(s => s.id === el.key);
      this.snowList.splice(snowIndex, 1);
      this.addSnow(); // 添加新的雪花
    }
  },
  mounted() {
    for (let i = 0; i < MAX_SNOW_NUM; i++) {
      this.addSnow();
    }
    setInterval(() => {
      this.snowList.length < MAX_SNOW_NUM && this.addSnow();
    }, 1000);
  }
}
</script>

<style scoped>
.snow-container {
  position: relative;
  width: 100%;
  height: 100%;
  overflow: hidden;
}

.snow {
  position: absolute;
  width: ${SNOW_SIZE}px;
  height: ${SNOW_SIZE}px;
  background-color: #fff;
  border-radius: 50%;
  opacity: 1;
  filter: blur(1px);
  pointer-events: none;
  z-index: 2;
  transition: all 1s ease-in-out;
}
.snow-enter-active,
.snow-leave-active {
  opacity: 1;
}
.snow-enter-to,
.snow-leave-from {
  opacity: 0;
}

</style>

这段代码使用了Vue的动画类库，通过`transition-group`来实现雪花的下落、消失、再显示。具体实现细节可以参考代码注释。