在做项目的时候，遇到了实现上下播放新闻的功能，

所以在次记录下实现原理

<template>
  <div :style="{height:60 + 'px'}" class="rollScreen_container" id="rollScreen_container">
    <div class="nav">
      <div class="nav_left">
        <img src="@/assets/laba.png" alt="">
        <span>新媒公告</span>
      </div>
      <div class="nav_right">
        <ul class="nav_ct" :style="transform" v-if="notice.length>0">
          <li v-for="(item,index) in notice" :key="index">{{item}}</li>
          <li>{{notice[0]}}</li>
        </ul>
      </div>
    </div>
  </div>
</template>
<script>
export default {
  props: {
    height: {
      default: 60,
      type: Number
    },
    lineNum: {
      default: 3,
      type: Number
    },
    notice: {
      default: function() {
        return [
          "我们来自同一个世界就发哦到附近",
          "我们都有爱的就发哦的及哦啊接发减肥减肥骄傲",
          "laizjfofjaodjfoajfdo"
        ];
      },
      type: Array
    }
  },
  data: function() {
    return {
      num: 0
    };
  },
  computed: {
    transform: function() {
        return "transform:translateY(-" + this.num * this.height + "px);";
    }
  },
  created: function() {
    this.init();
  },
  methods: {
    init() {
      let that = this;
      that.num += 1;
      let timeId = setInterval(function() {
        if (that.num == that.notice.length) { //判断num是否大于或等于notice的长度，让num为0，回到七点
          that.num = 0;
          clearInterval(timeId);  //清除定时器，防止时间停留两个3秒
          that.init();
        } else {
          that.num += 1;
        }
      }, 3000);
    }
  }
};
</script>

<style lang="less" scoped>
.rollScreen_container {
  width: 1200px;
  margin: 0 auto;
  margin-bottom: 20px;
  position: relative;
}

.nav {
  width: 1200px;
  margin: 0 auto;
  height: 60px;
  display: flex;
  justify-content: flex-start;
  align-items: center;
  background: #fff;
  padding: 0 40px;
  box-sizing: border-box;
  margin-bottom: 20px;

  .nav_left {
    display: flex;
    justify-content: flex-start;
    align-items: center;

    img {
      width: 25px;
      height: 20px;
    }

    span {
      font-size: 18px;
      font-weight: 600;
      color: #ec0504;
      margin-left: 20px;
    }
  }

  .nav_right {
    width: 80%;
    height: 60px;
    overflow: hidden;

    .nav_ct {
      width: 100%;
      margin-left: 60px;

      li {
        position: relative;
        width: 100%;
        height: 60px;
        line-height: 60px;
        display: flex;
        justify-content: flex-start;
        align-items: center;
        font-size: 15px;
        padding-left: 10px;
        box-sizing: border-box;
        font-weight: 600;
        overflow: hidden;
        text-overflow: ellipsis;
        white-space: nowrap;

        &:before {
          content: "";
          width: 5px;
          height: 5px;
          margin-right: 10px;
          border-radius: 50%;
          background: #000;
        }

        &:hover {
          cursor: pointer;
        }
      }
    }
  }
}
</style>