Vue transition组件简单实现数字滚动

<template>
  <button @click="addCount">点我滚动数字</button>
  <div class="roll-container">
    <transition name="roll">
      <div class="roll-number" :key="count">{{ count }}</div>
    </transition>
  </div>
</template>
<script>
import { defineComponent, ref } from 'vue';
export default defineComponent({
  setup() {
    const count = ref(0);
    let click_time = Date.now();
    function addCount() {
      if (Date.now() - click_time < 300) return;
      click_time = Date.now();
      count.value += 1;
    }
    return {
      count,
      addCount,
    };
  },
});
</script>
<style>
.roll-container {
  position: relative;
  text-align: center;
  font-size: 120px;
  line-height: 1em;
  color: #fff;
  height: 1em;
  min-width: 1em;
  max-width: 3em;
  background: #000000;
  overflow: hidden;
}
.roll-number {
  /* position: absolute; */
  /* top: 0; */
  width: 100%;
}
.roll-enter-active,
.roll-leave-active {
  transition: all .3s;
  position: absolute;
  top: 0;
}
.roll-leave-to {
  top: -1em;
}
.roll-enter-active {
  top: 1em;
}
.roll-enter-to {
  top: 0;
}
</style>
      

  <div class="roll-container">
    <transition name="roll">
      <div class="roll-number" :key="count">{{ count }}</div>
    </transition>
  </div>

.roll-container {
  position: relative;
  text-align: center;
  font-size: 120px;
  line-height: 1em;
  color: #fff;
  height: 1em;
  min-width: 1em;
  max-width: 3em;
  background: #000000;
  overflow: hidden;
}
.roll-number {
  width: 100%;
}

/* 
动画激活时给予初始状态，这个基础状态用于定义后续过渡动作的起点
这里统一定义了组件创建和组件销毁的两个起点，主要是赋予 transition 使其有一个过渡
*/
.roll-enter-active,
.roll-leave-active {
  transition: all .3s;
  position: absolute;
  top: 0;
}
/* 
组件销毁，过渡的终点
最开始的起点是原位，离开的时候滚到上面去
*/
.roll-leave-to {
  top: -1em;
}
/*
组件创建，过渡的起点
创建的时候是重下往上进入，所以元素最开始是在下面
*/
.roll-enter-active {
  top: 1em;
}
/*
过渡的时候回到起点，达到重下往上滚动
*/
.roll-enter-to {
  top: 0;
}

    const count = ref(0);
    // 缓存第一次状态修改的时间
    let click_time = Date.now();
    function addCount() {
      // 300ms 只能执行一次
      if (Date.now() - click_time < 300) return;
      // 重置状态修改的时间
      click_time = Date.now();
      count.value += 1;
    }