大文件上传和断点续传[转载]

原文地址:https://juejin.cn/post/6977555547570569223 作者:亦黑迷失

<template>
  <div id="app">
    <!-- 上传组件 -->
    <el-upload action drag :auto-upload="false" :show-file-list="false" :on-change="handleChange">
      <i class="el-icon-upload"></i>
      <div class="el-upload__text">将文件拖到此处,或<em>点击上传</em></div>
      <div class="el-upload__tip" slot="tip">大小不超过 200M 的视频</div>
    </el-upload>

    <!-- 进度显示 -->
    <div class="progress-box">
      <span>上传进度:{{ percent.toFixed() }}%</span>
      <el-button type="primary" size="mini" @click="handleClickBtn">{{ upload | btnTextFilter}}</el-button>
    </div>

    <!-- 展示上传成功的视频 -->
    <div v-if="videoUrl">
      <video :src="videoUrl" controls />
    </div>
  </div>
</template>

<script>
  import SparkMD5 from "spark-md5"
  import axios from "axios"

  export default {
    name: 'App3',
    filters: {
      btnTextFilter(val) {
        return val ? '暂停' : '继续'
      }
    },
    data() {
      return {
        percent: 0,
        videoUrl: '',
        upload: true,
        percentCount: 0
      }
    },
    methods: {
      async handleChange(file) {
        if (!file) return
        this.percent = 0
        this.videoUrl = ''
        // 获取文件并转成 ArrayBuffer 对象
        const fileObj = file.raw
        let buffer
        try {
          buffer = await this.fileToBuffer(fileObj)
        } catch (e) {
          console.log(e)
        }

        // 将文件按固定大小(2M)进行切片,注意此处同时声明了多个常量
        const chunkSize = 2097152,
          chunkList = [], // 保存所有切片的数组
          chunkListLength = Math.ceil(fileObj.size / chunkSize), // 计算总共多个切片
          suffix = /\.([0-9A-z]+)$/.exec(fileObj.name)[1] // 文件后缀名

        // 根据文件内容生成 hash 值
        const spark = new SparkMD5.ArrayBuffer()
        spark.append(buffer)
        const hash = spark.end()

        // 生成切片,这里后端要求传递的参数为字节数据块(chunk)和每个数据块的文件名(fileName)
        let curChunk = 0 // 切片时的初始位置
        for (let i = 0; i < chunkListLength; i++) {
          const item = {
            chunk: fileObj.slice(curChunk, curChunk + chunkSize),
            fileName: `${hash}_${i}.${suffix}` // 文件名规则按照 hash_1.jpg 命名
          }
          curChunk += chunkSize
          chunkList.push(item)
        }
        this.chunkList = chunkList // sendRequest 要用到
        this.hash = hash // sendRequest 要用到
        this.sendRequest()
      },

      // 发送请求
      sendRequest() {
        const requestList = [] // 请求集合
        this.chunkList.forEach((item, index) => {
          const fn = () => {
            const formData = new FormData()
            formData.append('chunk', item.chunk)
            formData.append('filename', item.fileName)
            return axios({
              url: '/single3',
              method: 'post',
              headers: { 'Content-Type': 'multipart/form-data' },
              data: formData
            }).then(res => {
              if (res.data.code === 0) { // 成功
                if (this.percentCount === 0) { // 避免上传成功后会删除切片改变 chunkList 的长度影响到 percentCount 的值
                  this.percentCount = 100 / this.chunkList.length
                }
                this.percent += this.percentCount // 改变进度
                this.chunkList.splice(index, 1) // 一旦上传成功就删除这一个 chunk,方便断点续传
              }
            })
          }
          requestList.push(fn)
        })

        let i = 0 // 记录发送的请求个数
        // 文件切片全部发送完毕后,需要请求 '/merge' 接口,把文件的 hash 传递给服务器
        const complete = () => {
          axios({
            url: '/merge',
            method: 'get',
            params: { hash: this.hash }
          }).then(res => {
            if (res.data.code === 0) { // 请求发送成功
              this.videoUrl = res.data.path
            }
          })
        }
        const send = async () => {
          if (!this.upload) return
          if (i >= requestList.length) {
            // 发送完毕
            complete()
            return
          } 
          await requestList[i]()
          i++
          send()
        }
        send() // 发送请求
      },

      // 按下暂停按钮
      handleClickBtn() {
        this.upload = !this.upload
        // 如果不暂停则继续上传
        if (this.upload) this.sendRequest()
      },

      // 将 File 对象转为 ArrayBuffer 
      fileToBuffer(file) {
        return new Promise((resolve, reject) => {
          const fr = new FileReader()
          fr.onload = e => {
            resolve(e.target.result)
          }
          fr.readAsArrayBuffer(file)
          fr.onerror = () => {
            reject(new Error('转换文件格式发生错误'))
          }
        })
      }
    }
  }
</script>

<style scoped>
  .progress-box {
    box-sizing: border-box;
    width: 360px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 10px;
    padding: 8px 10px;
    background-color: #ecf5ff;
    font-size: 14px;
    border-radius: 4px;
  }
</style>