<template>
  <div
    style="
      display: inline-flex;
      justify-content: flex-start;
      align-items: center;
    "
  >
    <div
      v-for="(item, index) in numberList"
      :key="index"
      style="
        display: inline-flex;
        justify-content: flex-start;
        align-items: center;
        padding-bottom: 0.3rem;
        box-sizing: border-box;
      "
    >
      <span v-if="isNaN(item)">{{ item }}</span>
      <div class="number" v-else>
        <span
          class="number-item"
          ref="numberItem"
          :data-number="item"
          :data-index="index"
          >0123456789</span
        >
      </div>
    </div>
  </div>
</template>
 
<script>
export default {
  name: "ScrollNumber",
  props: {
    value: {
      type: [String, Number],
      default: 0,
    },
  },
  watch: {
    value(newVal) {
      if (newVal) {
        this.$nextTick(() => {
          this.setNumberTransform();
        });
      }
    },
  },
  computed: {
    numberList() {
      return String(this.value).split("");
    },
  },
  data() {
    return {
      hasShow: false, // 是否已展示過動畫
    };
  },
  mounted() {
    window.addEventListener("scroll", this.scrollHandle, true); // 監(jiān)聽 監(jiān)聽元素是否進入/移出可視區(qū)域
  },
 
  methods: {
    scrollHandle() {
      const offset = this.$el.getBoundingClientRect();
      const offsetTop = offset.top;
      const offsetBottom = offset.bottom;
      // 進入可視區(qū)域
      if (offsetTop <= window.innerHeight && offsetBottom >= 0) {
        this.setNumberTransform();
        this.hasShow = true;
        window.removeEventListener("scroll", this.scrollHandle, true);
      } else {
        // 移出可視區(qū)域
        if (this.hasShow) {
          window.removeEventListener("scroll", this.scrollHandle, true);
        }
      }
    },
    // 設置每一位數(shù)字的偏移
    setNumberTransform() {
      let numberItems = this.$refs.numberItem;
      let obj = {};
      Array.from(numberItems).forEach((c) => {
        let key = c.dataset.index;
        let value = c.dataset.number;
        let init = 0;
        obj[key] = setInterval(() => {
          if (init < value * 10) {
            init += 1;
            c.style.transform = `translateY(-${init}%)`;
          } else {
            clearInterval(obj[key]);
            obj[key] = null;
          }
        }, 8);
      });
    },
  },
};
</script>
 
<style scoped lang="less">
.number {
  width: 0.42rem;
  height: 0.62rem;
  font-size: 0.56rem;
  font-weight: 800;
  color: #ffe52c;
  text-align: center;
  overflow: hidden;
  line-height: 0.42rem;
  > span {
    text-align: center;
    writing-mode: vertical-rl;
    text-orientation: upright;
    transform: translateY(0%);
  }
}
</style>

import ScrollNumber from "../ScrollNumber/ScrollNumber.vue";

<scroll-number :value="num.toString()"></scroll-number>