singleUpload function(file){
  let path = file.path; //文件本地路徑 
  let stats = fs.statSync(path);//讀取文件信息
  let chunkSize = 3*1024*1024;//每片分塊的大小3M
  let size = stats.size;//文件大小
  let pieces = Math.ceil(size / chunkSize);//總共的分片數(shù) 
  function uploadPiece (i){ 
    //計(jì)算每塊的結(jié)束位置
    let enddata = Math.min(size, (i + 1) * chunkSize);
    let arr = [];
    //創(chuàng)建一個(gè)readStream對象，根據(jù)文件起始位置和結(jié)束位置讀取固定的分片
    let readStream = fs.createReadStream(path, { start: i * chunkSize, end: enddata-1 });
      //on data讀取數(shù)據(jù)
      readStream.on(‘data‘, (data)=>{
        arr.push(data)
      }) 
      //on end在該分片讀取完成時(shí)觸發(fā)
      readStream.on(‘end‘, ()=>{
        //這里服務(wù)端只接受blob對象，需要把原始的數(shù)據(jù)流轉(zhuǎn)成blob對象，這塊為了配合后端才轉(zhuǎn)
        let blob = new Blob(arr)
        //新建formdata數(shù)據(jù)對象
        var formdata = new FormData();
        let md5Val = md5(Buffer.concat(arr));
        formdata.append("file", blob);
        console.log(‘blob.size‘,blob.size)
        formdata.append("md5", md5Val);
        formdata.append("size", size + ‘‘); // 數(shù)字30被轉(zhuǎn)換成字符串"30"
        formdata.append("chunk", i + ‘‘);//第幾個(gè)分片，從0開始
        formdata.append("chunks", pieces + ‘‘);//分片數(shù)
        formdata.append("name", name);//文件名
        post(formdata)//這里是偽代碼，實(shí)現(xiàn)上傳，開發(fā)者自己實(shí)現(xiàn)
  }
}