实现一个 Vue 吸顶锚点组件方法

.sticky-container {
 position: sticky;
 top: 0px;
}

// util.js 文件
// 判断一个元素是否是滚动元素
const scrollList = ['auto', 'scroll']

export function hasScrollElement(el, direction = 'vertical') {
 if (!el) return
 const style = window.getComputedStyle(el)
 if (direction === 'vertical') {
 return scrollList.includes(style.overflowY)
 } else if (direction === 'horizontal') {
 return scrollList.includes(style.overflowX)
 }
}

// 获取第一个滚动元素
export function getFirstScrollElement(el, direction = 'vertical') {
 if (!el) return
 if (hasScrollElement(el, direction)) {
 return el
 } else {
 return getFirstScrollElement(el && el.parentElement, direction)
 }
}

<template>
 <div class="cpt-sticky" :class="fixedClass" :style="{ top: top + 'px', zIndex }">
 <slot></slot>
 </div>
</template>

<script>
export default {
 props: {
 top: Number,
 parent: String,
 zIndex: Number
 },

 data() {
 return {
  fixedClass: '',
  scrollElement: null
 }
 },

 mounted() {
 this.initScrollElement()
 },

 destroyed() {
 this.removeScrollEvent()
 },

 methods: {
 handleScroll() {
  const scrollOffsetTop = this.$el.offsetTop - this.top
  if (this.scrollElement.scrollTop >= scrollOffsetTop) {
  this.fixedClass = 'top-fixed'
  } else {
  this.fixedClass = ''
  }
 },

 initScrollElement() {
  const element = document.querySelector(this.parent)
  if (element) {
  this.removeScrollEvent()
  this.scrollElement = element
  this.scrollElement.addEventListener('scroll', this.handleScroll)
  }
 }，

 removeScrollEvent() {
  if (this.scrollElement) {
  this.scrollElement.removeEventListener('scroll', this.handleScroll)
  }
 }
 }
}
</script>

<style lang="scss">
.cpt-sticky {
 .top-fixed {
 position: fixed;
 width: 100%;
 background: #fff;
 }
}
</style>

<template>
 <div class="cpt-sticky">
 <div class="sticky-container" :class="fixedClass" :style="{ top: top + 'px', zIndex }">
  <slot></slot>
 </div>
 <div v-if="showPlaceholder" class="sticky-placeholder" :style="{ height: offsetHeight + 'px' }"></div>
 </div>
</template>

<script>
import { getFirstScrollElement } from 'util.js'

export default {
 props: {
 top: {
  type: Number,
  default: 0
 },
 zIndex: {
  type: Number,
  default: 0
  },
 parent: {
  type: String,
  default: ''
 }
 },

 data() {
 return {
  isMounted: false,
  fixedClass: '',
  offsetHeight: 0,
  scrollElement: null,
  showPlaceholder: false
 }
 },

 mounted() {
 this.isMounted = true
 this.initScrollElement()
 },

 watch: {
 parent: {
  immediate: true,
  handler: 'getScrollElement'
 },

 fixedClass(v) {
  if (v && !this.offsetHeight) {
  this.offsetHeight = this.$el.offsetHeight
  }
  this.showPlaceholder = !!v
 }
 },

 destroyed() {
 this.removeScrollEvent()
 },

 methods: {
 handleScroll(e) {
  const scrollOffsetTop = this.$el.offsetTop - this.top
  if (this.scrollElement.scrollTop >= scrollOffsetTop) {
  this.fixedClass = 'top-fixed'
  } else {
  this.fixedClass = ''
  }
 },

 initScrollElement() {
  if (!this.isMounted) return
  const parent = this.parent
  let element = null
  if (parent) {
  element = document.querySelector(parent)
  if (element === this.scrollElement) return
  } else if (this.$el) {
  element = getFirstScrollElement(this.$el)
  }
  if (element) {
  this.removeScrollEvent()
  this.scrollElement = element
  this.scrollElement.addEventListener('scroll', this.handleScroll)
  }
 },

 removeScrollEvent() {
  if (this.scrollElement) {
  this.scrollElement.removeEventListener('scroll', this.handleScroll)
  }
 }
 }
}
</script>

<style lang="scss">
.cpt-sticky {
 .top-fixed {
 position: fixed;
 width: 100%;
 background: #fff;
 }
}
</style>

<a href="#view1">按钮1</a>
<a href="#view2">按钮1</a>
...
<div id="view1">视图1</div>
<div><a name="view2">视图2</a></div>

<template>
 <div class="cpt-anchor">
 <el-radio-group
  v-model="selector"
  size="mini"
  @change="handleMenuChange">
  <el-radio-button
  v-for="menu in menus"
  :key="menu.value"
  :label="menu.value">
  {{ menu.label }}
  </el-radio-button>
 </el-radio-group>
 </div>
</template>

<script>
// 添加缓动函数
import { tween } from 'shifty'
// 类似 lodash.get 但处理了 null 类型
import { get as _get } from 'noshjs'
import { getFirstScrollElement } from 'util.js'

export default {
 props: {
 // 滚动区距离可视区顶部的高度
 top: {
  type: Number,
  default: 0
 },
 menus: {
  type: Array,
  default: []
 }
 },

 data() {
 return {
  selector: ''
 }
 },

 watch: {
  menus: {
  immediate: true,
  handler(list) {
  this.selector = _get(list, [0, 'value'], '')
  }
 }
 },

 methods: {
 handleMenuChange(selector) {
  const scrollElement = document.querySelector(select)
  const rootScrollElement = getFirstScrollElement(scrollElement)
  if (scrollElement && rootScrollElement) {
  const offsetTop = scrollElement.offsetTop + scrollElement.clientTop
  const offsetHeight = _get(this.$el, ['parentElement', 'offsetHeight'], 0)
  const top = offsetTop - this.top - offsetHeight

  // 做一个缓动处理
  tween({
   from: { x: rootScrollElement.scrollTop },
   to: { x: top },
   duration: 500,
   easing: 'easeOutQuint',
   step: ({ x }) => {
   rootScrollElement.scrollTop = x
   }
  }).then(({ x }) => {
   rootScrollElement.scrollTop = x
  })
  }
 }
 }
}
</script>

<template>
 <div class="cpt-anchor">
 <el-radio-group
  v-model="selector"
  size="mini"
  @change="handleMenuChange">
  <el-radio-button
  v-for="menu in menus"
  :key="menu.value"
  :label="menu.value">
  {{ menu.label }}
  </el-radio-button>
 </el-radio-group>
 </div>
</template>

<script>
import { tween } from 'shifty'
import { get as _get } from 'noshjs'
import { getFirstScrollElement } from 'util.js'

import TabMenus from 'components/tab-menus.vue'

export default {
 props: {
 top: {
  type: Number,
  default: 0
 },
 menus: {
  type: Array,
  default: []
 },
 parent: {
  type: String,
  default: ''
 }
 },

 data() {
 return {
  menu: '',
  isScroll: true,
  isMounted: false,
  scrollTop: 0,
  anchorChange: false,
  rootScrollElement: ''
 }
 },

 mounted() {
 this.isMounted = true
 this.getScrollElement()
 },

 watch: {
 parent: {
  immediate: true,
  handler: 'getScrollElement'
 },

 menus: {
  immediate: true,
  handler(list) {
  this.menu = _get(list, [0, 'prop'], '')
  }
 },

 scrollTop(v) {
  if (this.anchorChange) {
  // 切换按钮会滚动视图，$nextTick 之后按钮值改变了，但滚动可能还没有结束，所以需要打个标记。
  this.isScroll = true
  }
 }
 },

 methods: {
 handleMenuChange(select) {
  this.isScroll = false
  this.anchorChange = false
  // 滚动高度等于元素距离可视区头部高度减去元素自身高度与元素上边框高度以及滚动区距离可视区头部的高度。
  const scrollElement = document.querySelector(select)
  if (scrollElement && this.rootScrollElement) {
  const offsetTop = scrollElement.offsetTop + scrollElement.clientTop
  const offsetHeight = _get(
   this.$el,
   ['parentElement', 'offsetHeight'],
   0
  )
  const top = offsetTop - this.top - offsetHeight

  // 做一个缓动处理
  tween({
   from: { x: this.rootScrollElement.scrollTop },
   to: { x: top },
   duration: 500,
   easing: 'easeOutQuint',
   step: ({ x }) => {
   this.rootScrollElement.scrollTop = x
   }
  }).then(({ x }) => {
   this.rootScrollElement.scrollTop = x
  })

  this.$nextTick(() => {
   this.anchorChange = true
  })
  }
 },

 getScrollElement() {
  if (!this.isMounted) return
  // 如果没有传入 parent 默认取第一个父级滚动元素
  const parent = this.parent
  let element = null
  if (parent) {
  element = document.querySelector(parent)
  // mount 之后 rootScrollElement 可能已经存在了，如果和上次一样就不做任何操作。
  if (element === this.rootScrollElement) return
  } else if (this.$el) {
  element = getFirstScrollElement(this.$el.parentElement)
  }
  if (element) {
  this.removeScrollEvent()
  this.rootScrollElement = element
  this.rootScrollElement.addEventListener('scroll', this.handleScroll)
  }
 },

 removeScrollEvent() {
  if (this.rootScrollElement) {
  this.rootScrollElement.removeEventListener('scroll', this.handleScroll)
  }
 },

 handleScroll(event) {
  const scrollTop = this.rootScrollElement.scrollTop
  this.scrollTop = scrollTop
  if (!this.isScroll) return
  const { data, top } = this
  const offsetHeight = _get(this.$el, ['parentElement', 'offsetHeight'], 0)
  const scrollList = []
  data.forEach(item => {
  const element = document.querySelector(item.prop)
  if (element) {
   const top = element.offsetTop
   const rect = {
   top: top + element.clientTop - top - offsetHeight,
   bottom: top + element.offsetHeight - top - offsetHeight
   }
   scrollList.push(rect)
  }
  })
  // 遍历按钮元素的 top 和 bottom，查看当前滚动在那个元素的区间内。
  scrollList.some((it, index) => {
  if (index && scrollTop >= it.top && top < it.bottom) {
   const menu = _get(data, [index, 'prop'], '')
   if (menu) this.menu = menu
   return true
  } else {
   // 当小于最小高度时，就等于最小高度
   if (scrollTop >= 0 && scrollTop < it.bottom) {
   const menu = _get(data, [index, 'prop'], '')
   if (menu) this.menu = menu
   return true
   }
  }
  })
 }
 }
}
</script>

<style lang="scss">
.cpt-anchor {
 padding-top: 4px;
 .cpt-tab-menus {
 margin: 0;
 .el-radio-button {
  margin-left: 10px;
  .el-radio-button__inner {
  border: none;
  border-radius: 5px 5px 0 0;
  border-bottom: 2px solid #e4e7ed;
  background-color: #f6f6f8;
  font-size: 16px;

  &:hover {
   border-bottom: 2px solid #409eff;
  }
  }

  &.is-active {
  .el-radio-button__inner {
   color: #fff;
   border: none;
   border-radius: 5px 5px 0 0;
   background-color: #409eff;
   border-bottom: 2px solid #409eff;
   box-shadow: none;
  }
  }
 }
 }
}
</style>

<template>
 <div class="cpt-sticky-anchor">
 <sticky :top="top" :z-index="zIndex">
  <sticky-menu :top="top" :data="menus" :parent="parent"></sticky-menu>
 </sticky>
 // 滚动区内容存放位置
 <slot></slot>
 </div>
</template>

<script>
import Sticky from './sticky.vue'
import StickyMenu from './menu.vue'

export default {
 // 这里简写了，因为上面已经有了。
 props: {
 top,
 menus,
 parent,
 zIndex,
 offsetHeight
 },

 components: {
 Sticky,
 StickyMenu
 }
}
</script>

<template>
 <div class="page-demo">
 ... 其他内容
 <sticky-anchor menus="menus" parent=".page-demo">
  <ul>
  <li class="button-1">视图一</li>
   <li class="button-2">视图二</li>
  </ul>
  </sticky-anchor>
 </div>
</template>

<script>
import StickyAnchor from 'components/sticky-anchor.vue'

export default {
 data() {
 return {
  menus: [
  { label: '按钮一', value: '.button-1' },
  { label: '按钮二', value: '.button-2' }
  ]
 }
 },

 components: {
 StickyAnchor
 }
}
</script>