分片分N次请求记录，包含重试控制，前端拼接总数据数组后导出

question:

1、如何控制每次并发的数量

2、promise 改写并发

一、同步版本

    
    async loopReqFile_sync (params) {
      //  199/30   0~6   7次，已默认请求第一次,1~6
      for (let i = 1; i < this.reqCount; i++) {
        params.start = i * this.downSize
        const { data } = await this.$api.audit.getNewRecordExcel_batch(params)
        this.fileData[i] = data.list
      }
      this.end = Date.now()
      console.log('cost time is', this.end - this.start)
      this.exportFileFunc()
      this.loading = false
    },

二、现在做到了并发请求，非promise版本

     

  handleExportExcel () {
      this.loading = true
      const formData = this.search.getFieldsValue()
      const _formData = omit(formData, ['start_end_time'])
      const params = {
        ..._formData,
        start_time: formData.start_end_time[0].format('YYYY-MM-DD HH:mm:ss'),
        end_time: formData.start_end_time[1].format('YYYY-MM-DD HH:mm:ss')
      }

      this.fileData = []
      this.retryObj = {}
      params.start = 0
      params.size = this.downSize
      // 第一次请求
      this.$api.audit
        .getNewRecordExcel_batch(params) // { responseType: 'blob' }
        .then(res => {
          const totalNum = res.data.count
          if (totalNum > 10000) {
            this.$message.info('请减少导出数量')
            this.loading = false
          } else {
            if (res.data.list.length > 0) {
              this.fileData[0] = res.data.list
              this.retryObj['file_0'] = 0 // 重试控制
              if (res.data.list.length < res.data.count) {
                // 第一次没有请求完数据
                this.reqCount = Math.ceil((res.data.count) / (this.downSize))
                this.start = Date.now()
                 // 剩下的请求
                this.loopReqFile_async(params)
              } else {
                this.loading = false
                this.exportFileFunc()
              }
            } else {
              this.$message.info('暂无数据')
              this.loading = false
            }
          }
        })
        .catch(() => {})
        .finally(() => {
        })
    },

    // 异步依次请求
    loopReqFile_async (params) {
      //  199/30   0~6   7次，已默认请求第一次,1~6
      this.realReqCount = 0
      for (let i = 1; i < this.reqCount; i++) {
        const j = i
        const reqObj = { ...params }
        reqObj.start = j * this.downSize
        this.retryObj['file_' + j] = 0


        setTimeout(() => {
          this.reqEveryFile(reqObj, j)
        }, j * 200)
      }
    },

   reqEveryFile (params, index) {
      // 异步并发
      this.$api.audit.getNewRecordExcel_batch(params).then(res => {
        this.fileData[index] = res.data.list
        this.realReqCount++
        if (this.realReqCount === (this.reqCount - 1)) {
          this.exportFileFunc()
          this.loading = false
          this.end = Date.now()
        }
      }).catch((e) => {
        if (this.retryObj['file_' + index] === 0) {
          this.reqEveryFile(params, index)
          this.retryObj['file_' + index] = this.retryObj['file_' + index] + 1
        }
      }).finally(() => {})
    },
 
 
   // 导出

    exportFileFunc () {
      let records = []
      for (let i = 0; i < this.fileData.length; i++) {
        records = records.concat(this.fileData[i])
      }


      const exportData = []
      const excludeEmt = ['nickname', 'mtime', 'action']
      const newColumns = this.columns.filter(item => excludeEmt.indexOf(item.dataIndex) === -1)
      console.log('newColumns', newColumns)
      exportData[0] = newColumns.map((item) => item.title)
      for (let j = 0; j < records.length; j++) {
        const tmpArr = newColumns.map((item) => {
          const crtKey = item.dataIndex
          let crtValue = records[j][crtKey]
          switch (crtKey) {
            case 'updated': crtValue = moment.unix(crtValue).format('YYYY-MM-DD HH:mm:ss')
          }
          return crtValue
        })
        exportData.push(tmpArr)
      }
 
      var workbook = new Excel.Workbook()
      var sheet = workbook.addWorksheet('Worksheet')
      sheet.addRows(exportData)
      workbook.xlsx.writeBuffer({ base64: true })
        .then(buffer => {
          var blob = new Blob([buffer], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' })
          var a = document.createElement('a')
          a.href = URL.createObjectURL(blob)
          a.download = `记录.xlsx`
          a.click()
          var dispose = () => URL.revokeObjectURL(blob)
          setTimeout(dispose, 100)
        })
    },

      

三、promise版本