实现效果如下  不管是点击还是  滚动鼠标 顶部的样式也会跟随变化

点击会跳转到指定的位置 

通过IntersectionObserver 监听是否可见 

下面代码可以直接执行到vue的文件 

<template>
  <div>
    <ul class="nav">
      <li v-for="tab in tabs" :key="tab.name" :class="{ active: currentTab === tab.name }" @click="scrollToTab(tab)">
        {{ tab.label }}
      </li>
      <div class="underline" :style="underlineStyle"></div>
    </ul>
    <div class="section" id="section1">Section 1</div>
    <div class="section" id="section2">Section 2</div>
    <div class="section" id="section3">Section 3</div>
    <div class="section" id="section4">Section 4</div>
    <div class="section" id="section5">Section 5</div>
  </div>
</template>

<script>
export default {
  data () {
    return {
      currentTab: 'tab1',
      tabs: [
        { name: 'tab1', label: '首页', id: 'section1' },
        { name: 'tab2', label: '服务内容', id: 'section2' },
        { name: 'tab3', label: '业务案例', id: 'section3' },
        { name: 'tab4', label: '关于我们', id: 'section4' },
        { name: 'tab5', label: '联系方式', id: 'section5' }
      ],
      underlineStyle: {
        width: '0px',
        left: '0px'
      }
    }
  },
  methods: {
    scrollToTab (section) {
      this.currentTab = section.name
      this.updateUnderline()
      const element = document.getElementById(section.id)
      document.getElementById(section.id).scrollIntoView({ behavior: 'smooth', block: 'center' })
    },
    updateUnderline () {
      this.$nextTick(() => {
        const activeTab = this.$el.querySelector('.nav .active')
        if (activeTab) {
          this.underlineStyle.width = `${activeTab.offsetWidth}px`
          this.underlineStyle.left = `${activeTab.offsetLeft}px`
        }
      })
    },
    handleIntersection (entries) {
      entries.forEach((entry) => {
        if (entry.isIntersecting) {
          const tab = this.tabs.find((tab) => tab.id === entry.target.id)
          if (tab) {
            this.currentTab = tab.name
            this.updateUnderline()
          }
        }
      })
    }
  },
  mounted () {
    this.updateUnderline()
    const options = {
      root: null,
      rootMargin: `-${this.$el.querySelector('.nav').offsetHeight}px 0px 0px 0px`,
      threshold: 0.5
    }

    const observer = new IntersectionObserver(this.handleIntersection, options)
    this.tabs.forEach((tab) => {
      const section = document.getElementById(tab.id)
      if (section) {
        observer.observe(section)
      }
    })

    window.addEventListener('resize', this.updateUnderline)
  },
  beforeDestroy () {
    window.removeEventListener('resize', this.updateUnderline)
  }
}
</script>

<style scoped>
.nav {
  display: flex;
  position: fixed;
  top: 0;
  width: 1000px;
  background-color: white;
  z-index: 1000;
  border-bottom: 1px solid #ccc;
}
.nav li {
  flex: 1;
  text-align: center;
  padding: 10px;
  cursor: pointer;
  position: relative;
}
.nav li.active {
  color: blue;
}
.underline {
  position: absolute;
  bottom: 0;
  height: 2px;
  background-color: blue;
  transition: width 0.3s, left 0.3s;
}
.section {
  height: 300px;
  padding-top: 60px; /* 留出导航栏的高度 */
  border-bottom: 1px solid #ccc;
}
</style>