不多bb，直接开整
定义变量
const demo = ref(null) // 外框盒子
const showNumber = 20 // 当前视窗展示条数
const itemHeight = 20 // 每一条内容的高度
const data = createData(1000) // 实际数据
let startNum = ref(0) // 当前视窗范围内第一个元素下标
let positionTop = ref(0) // 当前视窗范围内第一个元素偏移量
复制代码滚动
虚拟滚动第一条件首先是要能滚动，那么外框盒子高度固定，设置overflow: auto;
<div
ref="demo"
class="scroll-box demo"
:style="`height: ${showNumber * itemHeight}px;`"
></div>
复制代码然后外框盒子内部内置一个高度为理论上渲染全部内容的空div占位，用于展示滚动条
<div
class="scroll-blank"
:style="`height: ${data.length * itemHeight}px;`"
></div>
复制代码虚拟
虚拟就是仅渲染当前视窗内的内容，而对于超出的部分则进行移除
<template>
<div class="scroll-data" :style="`top: ${positionTop}px;`">
<div
v-for="(item, index) in activeList"
:key="item"
class="scroll-item"
>
{{ item }}
</div>
</div>
</template>
<script>
const activeList = computed(() => {
const start = startNum.value
return data.slice(start, start + showNumber)
})
</script>
复制代码什么时候对渲染的数据进行替换？
对外框盒子添加 scroll 的监听事件，在滚动的时候获取scrollTop的值并计算当前视窗范围内第一个元素的下标
const scrollEvent = (event) => {
const { scrollTop } = event.target
startNum.value = parseInt(scrollTop / itemHeight)
positionTop.value = scrollTop
}
onMounted(() => {
demo.value.addEventListener('scroll', scrollEvent)
})
onUnmounted(() => {
if (!demo.value) return
demo.value.removeEventListener('scroll', scrollEvent)
demo.value = null
})
复制代码最后
贴上完整demo
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<script src="https://unpkg.com/[email protected]/dist/vue.global.js"></script>
<title>VirtualScroll</title>
</head>
<body>
<div id="app">
<div
ref="demo"
class="scroll-box demo"
:style="`height: ${showNumber * itemHeight}px;`"
>
<div
class="scroll-blank"
:style="`height: ${data.length * itemHeight}px;`"
></div>
<div class="scroll-data" :style="`top: ${positionTop}px;`">
<div
v-for="(item, index) in activeList"
:key="item"
class="scroll-item"
>
{{ item }}
</div>
</div>
</div>
</div>
<script>
const { computed, onMounted, onUnmounted, ref } = Vue
const createData = (length) => {
return Object.keys(new Array(length).fill(''))
}
const App = {
setup() {
const demo = ref(null) // 外框盒子
const showNumber = 20 // 当前视窗展示条数
const itemHeight = 20 // 每一条内容的高度
const data = createData(1000) // 实际数据
let startNum = ref(0) // 当前视窗范围内第一个元素下标
let positionTop = ref(0) // 当前视窗范围内第一个元素偏移量
// 计算当前视窗内实际要渲染的内容
const activeList = computed(() => {
const start = startNum.value
return data.slice(start, start + showNumber)
})
// 滚动的时候计算当前视窗范围内第一个元素下标
const scrollEvent = (event) => {
const { scrollTop } = event.target
startNum.value = parseInt(scrollTop / itemHeight)
positionTop.value = scrollTop
}
onMounted(() => {
demo.value.addEventListener('scroll', scrollEvent)
})
onUnmounted(() => {
if (!demo.value) return
demo.value.removeEventListener('scroll', scrollEvent)
demo.value = null
})
return {
showNumber,
itemHeight,
demo,
positionTop,
data,
activeList,
}
},
}
const app = Vue.createApp(App)
app.mount('#app')
</script>
<style>
.scroll-box {
position: relative;
overflow: auto;
width: 400px;
border: 1px solid rgb(0, 0, 0);
}
.scroll-data {
position: absolute;
width: 100%;
}
.scroll-item {
height: 20px;
}
.scroll-item:hover {
background: rgb(104, 111, 211);
color: #fff;
}
</style>
</body>
</html>
复制代码