VUE3--实现CountTo数字滚动组件（vite2+vue3.2.x）

概要

基础组件开发是项目业务开发的基石, 本文主要介绍了通过vue3+vite2快速搭建项目, 实现数字滚动组件。

初始化项目

使用npm执行以下命令:

npm init vite@latest

按照操作提示进行操作即可

配置vite.config.js

import { defineConfig } from 'vite'
import vue from '@vitejs/plugin-vue'
import path from 'path'

// https://vitejs.dev/config/
export default defineConfig({
  plugins: [vue()],
  resolve: {
    alias: {
      '@': path.resolve(__dirname, './src'),
      'public': path.resolve(__dirname, './public')
    }
  }
})

按照下图创建目录结构：

开发计数组件功能代码

requestAnimationFrame.js代码

requestAnimationFrame 是专门为实现高性能的帧动画而设计的一个API，requestAnimationFrame 比起 setTimeout、setInterval的优势主要有两点：
1、requestAnimationFrame 会把每一帧中的所有DOM操作集中起来，在一次重绘或回流中就完成，并且重绘或回流的时间间隔紧紧跟随浏览器的刷新频率，一般来说，这个频率为每秒60帧。
2、在隐藏或不可见的元素中，requestAnimationFrame将不会进行重绘或回流，这当然就意味着更少的的cpu，gpu和内存使用量。

let lastTime = 0
const prefixes = 'webkit moz ms o'.split(' ') // 各浏览器前缀

let requestAnimationFrame
let cancelAnimationFrame

// 判断是否是服务器环境
const isServer = typeof window === 'undefined'
if (isServer) {
  requestAnimationFrame = function() {
    return
  }
  cancelAnimationFrame = function() {
    return
  }
} else {
  requestAnimationFrame = window.requestAnimationFrame
  cancelAnimationFrame = window.cancelAnimationFrame
  let prefix
    // 通过遍历各浏览器前缀，来得到requestAnimationFrame和cancelAnimationFrame在当前浏览器的实现形式
  for (let i = 0; i < prefixes.length; i++) {
    if (requestAnimationFrame && cancelAnimationFrame) { break }
    prefix = prefixes[i]
    requestAnimationFrame = requestAnimationFrame || window[prefix + 'RequestAnimationFrame']
    cancelAnimationFrame = cancelAnimationFrame || window[prefix + 'CancelAnimationFrame'] || window[prefix + 'CancelRequestAnimationFrame']
  }

  // 如果当前浏览器不支持requestAnimationFrame和cancelAnimationFrame，则会退到setTimeout
  if (!requestAnimationFrame || !cancelAnimationFrame) {
    requestAnimationFrame = function(callback) {
      const currTime = new Date().getTime()
      // 为了使setTimteout的尽可能的接近每秒60帧的效果
      const timeToCall = Math.max(0, 16 - (currTime - lastTime))
      const id = window.setTimeout(() => {
        callback(currTime + timeToCall)
      }, timeToCall)
      lastTime = currTime + timeToCall
      return id
    }

    cancelAnimationFrame = function(id) {
      window.clearTimeout(id)
    }
  }
}

export { requestAnimationFrame, cancelAnimationFrame }

CountTO.vue代码

计数组件的主要功能实现部分

<template>
  {{ state.displayValue }}
</template>

<script setup>  // vue3.2新的语法糖, 编写代码更加简洁高效
import { onMounted, onUnmounted, reactive } from "@vue/runtime-core";
import { watch, computed } from 'vue';
import { requestAnimationFrame, cancelAnimationFrame } from './requestAnimationFrame.js'
// 定义父组件传递的参数
const props = defineProps({
  start: {
    type: Number,
    required: false,
    default: 0
  },
  end: {
    type: Number,
    required: false,
    default: 2021
  },
  duration: {
    type: Number,
    required: false,
    default: 5000
  },
  autoPlay: {
    type: Boolean,
    required: false,
    default: true
  },
  decimals: {
    type: Number,
    required: false,
    default: 0,
    validator (value) {
      return value >= 0
    }
  },
  decimal: {
    type: String,
    required: false,
    default: '.'
  },
  separator: {
    type: String,
    required: false,
    default: ','
  },
  prefix: {
    type: String,
    required: false,
    default: ''
  },
  suffix: {
    type: String,
    required: false,
    default: ''
  },
  useEasing: {
    type: Boolean,
    required: false,
    default: true
  },
  easingFn: {
    type: Function,
    default(t, b, c, d) {
      return c * (-Math.pow(2, -10 * t / d) + 1) * 1024 / 1023 + b;
    }
  }
})

const isNumber = (val) => {
  return !isNaN(parseFloat(val))
}

// 格式化数据，返回想要展示的数据格式
const formatNumber = (val) => {
  val = val.toFixed(props.default)
  val += ''
  const x = val.split('.')
  let x1 = x[0]
  const x2 = x.length > 1 ? props.decimal + x[1] : ''
  const rgx = /(\d+)(\d{3})/
  if (props.separator && !isNumber(props.separator)) {
    while (rgx.test(x1)) {
      x1 = x1.replace(rgx, '$1' + props.separator + '$2')
    }
  }
  return props.prefix + x1 + x2 + props.suffix
}

// 相当于vue2中的data中所定义的变量部分
const state = reactive({
  localStart: props.start,
  displayValue: formatNumber(props.start),
  printVal: null,
  paused: false,
  localDuration: props.duration,
  startTime: null,
  timestamp: null,
  remaining: null,
  rAF: null
})

// 定义一个计算属性，当开始数字大于结束数字时返回true
const stopCount = computed(() => {
  return props.start > props.end
})
// 定义父组件的自定义事件，子组件以触发父组件的自定义事件
const emits = defineEmits(['onMountedcallback', 'callback'])

const startCount = () => {
  state.localStart = props.start
  state.startTime = null
  state.localDuration = props.duration
  state.paused = false
  state.rAF = requestAnimationFrame(count)
}

watch(() => props.start, () => {
  if (props.autoPlay) {
    startCount()
  }
})

watch(() => props.end, () => {
  if (props.autoPlay) {
    startCount()
  }
})
// dom挂在完成后执行一些操作
onMounted(() => {
  if (props.autoPlay) {
    startCount()
  }
  emits('onMountedcallback')
})
// 暂停计数
const pause = () => {
  cancelAnimationFrame(state.rAF)
}
// 恢复计数
const resume = () => {
  state.startTime = null
  state.localDuration = +state.remaining
  state.localStart = +state.printVal
  requestAnimationFrame(count)
}

const pauseResume = () => {
  if (state.paused) {
    resume()
    state.paused = false
  } else {
    pause()
    state.paused = true
  }
}

const reset = () => {
  state.startTime = null
  cancelAnimationFrame(state.rAF)
  state.displayValue = formatNumber(props.start)
}

const count = (timestamp) => {
  if (!state.startTime) state.startTime = timestamp
  state.timestamp = timestamp
  const progress = timestamp - state.startTime
  state.remaining = state.localDuration - progress
  // 是否使用速度变化曲线
  if (props.useEasing) {
    if (stopCount.value) {
      state.printVal = state.localStart - props.easingFn(progress, 0, state.localStart - props.end, state.localDuration)
    } else {
      state.printVal = props.easingFn(progress, state.localStart, props.end - state.localStart, state.localDuration)
    }
  } else {
    if (stopCount.value) {
      state.printVal = state.localStart - ((state.localStart - props.end) * (progress / state.localDuration))
    } else {
      state.printVal = state.localStart + (props.end - state.localStart) * (progress / state.localDuration)
    }
  }
  if (stopCount.value) {
    state.printVal = state.printVal < props.end ? props.end : state.printVal
  } else {
    state.printVal = state.printVal > props.end ? props.end : state.printVal
  }

  state.displayValue = formatNumber(state.printVal)
  if (progress < state.localDuration) {
    state.rAF = requestAnimationFrame(count)
  } else {
    emits('callback')
  }
}
// 组件销毁时取消动画
onUnmounted(() => {
  cancelAnimationFrame(state.rAF)
})
</script>

组件库的出口index.js代码

导出一个含有install方法的对象，用来全局注册组件

import CountTo from './count-to/CountTo.vue'

const UILib  = {
  install (Vue) {
    Vue.component('CountTo', CountTo)
  }
}

export default UILib

在main.js全局注册组件

import { createApp } from 'vue'
import App from './App.vue'
import UILib from './components/ui-lib/index'

const app = createApp(App)
app.use(UILib)
app.mount('#app')

在App.vue中调用组件

<template>
  <h1>Hello Vite</h1>
  <CountTo :start='start' :end='end' prefix="￥" suffix="rmb" :autoPlay="true" :duration='3000' />
</template>

<script setup>
import { ref } from '@vue/runtime-core';
const start = ref(0)
const end = ref(2021)
</script>

<style>
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
</style>

效果

运行npm run dev，计数效果如下