参考代码： wx-formdata
问题是：上传文件数据流时，传参方式是：formData.appendFile(name, filepath)，不能满足将一条数据分片上传的需求。看了源代码后，发现this.appendFile这个方法。

  this.appendFile = (name, path) => {
    let buffer = fileManager.readFileSync(path)
    if (Object.prototype.toString.call(buffer).indexOf('ArrayBuffer') < 0) {
      return false
    }
    files.push({
      name: name,
      buffer: buffer,
      fileName: getFileNameFromPath(path)
    })
    return true
  }

改装后，将buffer从外面传入

  this.appendFile = (name, buffer, path) => {
    // let buffer = fileManager.readFileSync(path);
    // if(Object.prototype.toString.call(buffer).indexOf("ArrayBuffer") < 0){
    //   return false;
    // }
    files.push({
      name: name,
      buffer: buffer,
      fileName: getFileNameFromPath(path)
    })
    return true
  }

wx-formdata

在小程序中使用 formdata 上传数据，可实现多文件上传

用法

跟浏览器中的 FormData 对象类似
引入 js 文件

const FormData = require('./formData.js')

new 一个 FormData 对象

let formData = new FormData()

调用它的append()方法来添加字段或者调用appendFile()方法添加文件

formData.append('name', 'value')
formData.appendFile('file', name, file, filepath)

添加完成后调用它的getData()生成上传数据，之后调用axios 提交请求

let data = formData.getData()
$httpRequest2 = axios.create({
  withCredentials: true,
  crossDomain: true,
  baseURL: '',
  timeout: 6000
})
$httpRequest2({
  url: 'https://接口地址',
  method: 'POST',
  header: {
    'content-type': data.contentType
  },
  data: data.buffer
}).then(res=>{
    console.log('分片成功请求：',res)
}) .catch(err => {
          console.log('分片上传失败：', err)
})

成员函数

FormData.append()

语法

formData.append(name, value)

参数

参数名	描述
name	value 中包含的数据对应的表单名称
value	表单的值

FormData.appendFile()

语法

formData.appendFile(name, file, filepath)

参数

参数名	描述
name	value 中包含的数据对应的表单名称
file	文件流 （file 格式或者二进制流都可以）
filepath	文件路径

FormData.getData()

语法

let data = formData.getData()

返回值对象属性

属性名	描述
buffer	表单数据的 ArrayBuffer 对象
contentType	http 请求 Content-Type 头部内容

结构：

wx-formdata
|——formData.js
|——mimeType.js

formData.js

const mimeMap = require('./mimeMap.js')

function FormData() {
  let fileManager = wx.getFileSystemManager()
  let data = {}
  let files = []

  this.append = (name, value) => {
    data[name] = value
    return true
  }

  this.appendFile = (name, buffer, path) => {
    // let buffer = fileManager.readFileSync(path);
    // if(Object.prototype.toString.call(buffer).indexOf("ArrayBuffer") < 0){
    //   return false;
    // }
    files.push({
      name: name,
      buffer: buffer,
      fileName: getFileNameFromPath(path)
    })
    return true
  }

  this.getData = () => convert(data, files)
}

function getFileNameFromPath(path) {
  let idx = path.lastIndexOf('/')
  return path.substr(idx + 1)
}

function convert(data, files) {
  let boundaryKey = 'wxmpFormBoundary' + randString() // 数据分割符，一般是随机的字符串
  let boundary = '--' + boundaryKey
  let endBoundary = boundary + '--'

  let postArray = []
  //拼接参数
  if (data && Object.prototype.toString.call(data) == '[object Object]') {
    for (let key in data) {
      postArray = postArray.concat(formDataArray(boundary, key, data[key]))
    }
  }
  //拼接文件
  if (files && Object.prototype.toString.call(files) == '[object Array]') {
    for (let i in files) {
      let file = files[i]
      postArray = postArray.concat(
        formDataArray(boundary, file.name, file.buffer, file.fileName)
      )
    }
  }
  //结尾
  let endBoundaryArray = []
  for (var i = 0; i < endBoundary.length; i++) {
    // 最后取出结束boundary的charCode
    endBoundaryArray.push(...endBoundary.utf8CodeAt(i))
  }
  postArray = postArray.concat(endBoundaryArray)
  return {
    contentType: 'multipart/form-data; boundary=' + boundaryKey,
    buffer: new Uint8Array(postArray).buffer
  }
}

function randString() {
  let res = ''
  for (let i = 0; i < 17; i++) {
    let n = parseInt(Math.random() * 62)
    if (n <= 9) {
      res += n
    } else if (n <= 35) {
      res += String.fromCharCode(n + 55)
    } else {
      res += String.fromCharCode(n + 61)
    }
  }
  return res
}

function formDataArray(boundary, name, value, fileName) {
  let dataString = ''
  let isFile = !!fileName

  dataString += boundary + '\r\n'
  dataString += 'Content-Disposition: form-data; name="' + name + '"'
  if (isFile) {
    dataString += '; filename="' + fileName + '"' + '\r\n'
    dataString += 'Content-Type: ' + getFileMime(fileName) + '\r\n\r\n'
  } else {
    dataString += '\r\n\r\n'
    dataString += value
  }

  var dataArray = []
  for (var i = 0; i < dataString.length; i++) {
    // 取出文本的charCode（10进制）
    dataArray.push(...dataString.utf8CodeAt(i))
  }

  if (isFile) {
    let fileArray = new Uint8Array(value)
    dataArray = dataArray.concat(Array.prototype.slice.call(fileArray))
  }
  dataArray.push(...'\r'.utf8CodeAt())
  dataArray.push(...'\n'.utf8CodeAt())

  return dataArray
}

function getFileMime(fileName) {
  let idx = fileName.lastIndexOf('.')
  let mime = mimeMap[fileName.substr(idx)]
  return mime ? mime : 'application/octet-stream'
}

String.prototype.utf8CodeAt = function(i) {
  var str = this
  var out = [],
    p = 0
  var c = str.charCodeAt(i)
  if (c < 128) {
    out[p++] = c
  } else if (c < 2048) {
    out[p++] = (c >> 6) | 192
    out[p++] = (c & 63) | 128
  } else if (
    (c & 0xfc00) == 0xd800 &&
    i + 1 < str.length &&
    (str.charCodeAt(i + 1) & 0xfc00) == 0xdc00
  ) {
    // Surrogate Pair
    c = 0x10000 + ((c & 0x03ff) << 10) + (str.charCodeAt(++i) & 0x03ff)
    out[p++] = (c >> 18) | 240
    out[p++] = ((c >> 12) & 63) | 128
    out[p++] = ((c >> 6) & 63) | 128
    out[p++] = (c & 63) | 128
  } else {
    out[p++] = (c >> 12) | 224
    out[p++] = ((c >> 6) & 63) | 128
    out[p++] = (c & 63) | 128
  }
  return out
}

module.exports = FormData

mimeMap.js

module.exports = {
  "0.001": "application/x-001",
  "0.323": "text/h323",
  "0.907": "drawing/907",
  ".acp": "audio/x-mei-aac",
  ".aif": "audio/aiff",
  ".aiff": "audio/aiff",
  ".asa": "text/asa",
  ".asp": "text/asp",
  ".au": "audio/basic",
  ".awf": "application/vnd.adobe.workflow",
  ".bmp": "application/x-bmp",
  ".c4t": "application/x-c4t",
  ".cal": "application/x-cals",
  ".cdf": "application/x-netcdf",
  ".cel": "application/x-cel",
  ".cg4": "application/x-g4",
  ".cit": "application/x-cit",
  ".cml": "text/xml",
  ".cmx": "application/x-cmx",
  ".crl": "application/pkix-crl",
  ".csi": "application/x-csi",
  ".cut": "application/x-cut",
  ".dbm": "application/x-dbm",
  ".dcd": "text/xml",
  ".der": "application/x-x509-ca-cert",
  ".dib": "application/x-dib",
  ".doc": "application/msword",
  ".drw": "application/x-drw",
  ".dwf": "Model/vnd.dwf",
  ".dwg": "application/x-dwg",
  ".dxf": "application/x-dxf",
  ".emf": "application/x-emf",
  ".ent": "text/xml",
  ".eps": "application/x-ps",
  ".etd": "application/x-ebx",
  ".fax": "image/fax",
  ".fif": "application/fractals",
  ".frm": "application/x-frm",
  ".gbr": "application/x-gbr",
  ".gif": "image/gif",
  ".gp4": "application/x-gp4",
  ".hmr": "application/x-hmr",
  ".hpl": "application/x-hpl",
  ".hrf": "application/x-hrf",
  ".htc": "text/x-component",
  ".html": "text/html",
  ".htx": "text/html",
  ".ico": "image/x-icon",
  ".iff": "application/x-iff",
  ".igs": "application/x-igs",
  ".img": "application/x-img",
  ".isp": "application/x-internet-signup",
  ".java": "java/*",
  ".jpe": "image/jpeg",
  ".jpeg": "image/jpeg",
  ".jpg": "application/x-jpg",
  ".jsp": "text/html",
  ".lar": "application/x-laplayer-reg",
  ".lavs": "audio/x-liquid-secure",
  ".lmsff": "audio/x-la-lms",
  ".ltr": "application/x-ltr",
  ".m2v": "video/x-mpeg",
  ".m4e": "video/mpeg4",
  ".man": "application/x-troff-man",
  ".mdb": "application/msaccess",
  ".mfp": "application/x-shockwave-flash",
  ".mhtml": "message/rfc822",
  ".mid": "audio/mid",
  ".mil": "application/x-mil",
  ".mnd": "audio/x-musicnet-download",
  ".mocha": "application/x-javascript",
  ".mp1": "audio/mp1",
  ".mp2v": "video/mpeg",
  ".mp4": "video/mpeg4",
  ".mpd": "application/vnd.ms-project",
  ".mpeg": "video/mpg",
  ".mpga": "audio/rn-mpeg",
  ".mps": "video/x-mpeg",
  ".mpv": "video/mpg",
  ".mpw": "application/vnd.ms-project",
  ".mtx": "text/xml",
  ".net": "image/pnetvue",
  ".nws": "message/rfc822",
  ".out": "application/x-out",
  ".p12": "application/x-pkcs12",
  ".p7c": "application/pkcs7-mime",
  ".p7r": "application/x-pkcs7-certreqresp",
  ".pc5": "application/x-pc5",
  ".pcl": "application/x-pcl",
  ".pdf": "application/pdf",
  ".pdx": "application/vnd.adobe.pdx",
  ".pgl": "application/x-pgl",
  ".pko": "application/vnd.ms-pki.pko",
  ".plg": "text/html",
  ".plt": "application/x-plt",
  ".png": "application/x-png",
  ".ppa": "application/vnd.ms-powerpoint",
  ".pps": "application/vnd.ms-powerpoint",
  ".ppt": "application/x-ppt",
  ".prf": "application/pics-rules",
  ".prt": "application/x-prt",
  ".ps": "application/postscript",
  ".pwz": "application/vnd.ms-powerpoint",
  ".ra": "audio/vnd.rn-realaudio",
  ".ras": "application/x-ras",
  ".rdf": "text/xml",
  ".red": "application/x-red",
  ".rjs": "application/vnd.rn-realsystem-rjs",
  ".rlc": "application/x-rlc",
  ".rm": "application/vnd.rn-realmedia",
  ".rmi": "audio/mid",
  ".rmm": "audio/x-pn-realaudio",
  ".rms": "application/vnd.rn-realmedia-secure",
  ".rmx": "application/vnd.rn-realsystem-rmx",
  ".rp": "image/vnd.rn-realpix",
  ".rsml": "application/vnd.rn-rsml",
  ".rtf": "application/msword",
  ".rv": "video/vnd.rn-realvideo",
  ".sat": "application/x-sat",
  ".sdw": "application/x-sdw",
  ".slb": "application/x-slb",
  ".slk": "drawing/x-slk",
  ".smil": "application/smil",
  ".snd": "audio/basic",
  ".sor": "text/plain",
  ".spl": "application/futuresplash",
  ".ssm": "application/streamingmedia",
  ".stl": "application/vnd.ms-pki.stl",
  ".sty": "application/x-sty",
  ".swf": "application/x-shockwave-flash",
  ".tg4": "application/x-tg4",
  ".tif": "image/tiff",
  ".tiff": "image/tiff",
  ".top": "drawing/x-top",
  ".tsd": "text/xml",
  ".uin": "application/x-icq",
  ".vcf": "text/x-vcard",
  ".vdx": "application/vnd.visio",
  ".vpg": "application/x-vpeg005",
  ".vsd": "application/x-vsd",
  ".vst": "application/vnd.visio",
  ".vsw": "application/vnd.visio",
  ".vtx": "application/vnd.visio",
  ".wav": "audio/wav",
  ".wb1": "application/x-wb1",
  ".wb3": "application/x-wb3",
  ".wiz": "application/msword",
  ".wk4": "application/x-wk4",
  ".wks": "application/x-wks",
  ".wma": "audio/x-ms-wma",
  ".wmf": "application/x-wmf",
  ".wmv": "video/x-ms-wmv",
  ".wmz": "application/x-ms-wmz",
  ".wpd": "application/x-wpd",
  ".wpl": "application/vnd.ms-wpl",
  ".wr1": "application/x-wr1",
  ".wrk": "application/x-wrk",
  ".ws2": "application/x-ws",
  ".wsdl": "text/xml",
  ".xdp": "application/vnd.adobe.xdp",
  ".xfd": "application/vnd.adobe.xfd",
  ".xhtml": "text/html",
  ".xls": "application/x-xls",
  ".xml": "text/xml",
  ".xq": "text/xml",
  ".xquery": "text/xml",
  ".xsl": "text/xml",
  ".xwd": "application/x-xwd",
  ".sis": "application/vnd.symbian.install",
  ".x_t": "application/x-x_t",
  ".apk": "application/vnd.android.package-archive",
  "0.301": "application/x-301",
  "0.906": "application/x-906",
  ".a11": "application/x-a11",
  ".ai": "application/postscript",
  ".aifc": "audio/aiff",
  ".anv": "application/x-anv",
  ".asf": "video/x-ms-asf",
  ".asx": "video/x-ms-asf",
  ".avi": "video/avi",
  ".biz": "text/xml",
  ".bot": "application/x-bot",
  ".c90": "application/x-c90",
  ".cat": "application/vnd.ms-pki.seccat",
  ".cdr": "application/x-cdr",
  ".cer": "application/x-x509-ca-cert",
  ".cgm": "application/x-cgm",
  ".class": "java/*",
  ".cmp": "application/x-cmp",
  ".cot": "application/x-cot",
  ".crt": "application/x-x509-ca-cert",
  ".css": "text/css",
  ".dbf": "application/x-dbf",
  ".dbx": "application/x-dbx",
  ".dcx": "application/x-dcx",
  ".dgn": "application/x-dgn",
  ".dll": "application/x-msdownload",
  ".dot": "application/msword",
  ".dtd": "text/xml",
  ".dwf": "application/x-dwf",
  ".dxb": "application/x-dxb",
  ".edn": "application/vnd.adobe.edn",
  ".eml": "message/rfc822",
  ".epi": "application/x-epi",
  ".eps": "application/postscript",
  ".exe": "application/x-msdownload",
  ".fdf": "application/vnd.fdf",
  ".fo": "text/xml",
  ".g4": "application/x-g4",
  ".tif": "image/tiff",
  ".gl2": "application/x-gl2",
  ".hgl": "application/x-hgl",
  ".hpg": "application/x-hpgl",
  ".hqx": "application/mac-binhex40",
  ".hta": "application/hta",
  ".htm": "text/html",
  ".htt": "text/webviewhtml",
  ".icb": "application/x-icb",
  ".ico": "application/x-ico",
  ".ig4": "application/x-g4",
  ".iii": "application/x-iphone",
  ".ins": "application/x-internet-signup",
  ".IVF": "video/x-ivf",
  ".jfif": "image/jpeg",
  ".jpe": "application/x-jpe",
  ".jpg": "image/jpeg",
  ".js": "application/x-javascript",
  ".la1": "audio/x-liquid-file",
  ".latex": "application/x-latex",
  ".lbm": "application/x-lbm",
  ".ls": "application/x-javascript",
  ".m1v": "video/x-mpeg",
  ".m3u": "audio/mpegurl",
  ".mac": "application/x-mac",
  ".math": "text/xml",
  ".mdb": "application/x-mdb",
  ".mht": "message/rfc822",
  ".mi": "application/x-mi",
  ".midi": "audio/mid",
  ".mml": "text/xml",
  ".mns": "audio/x-musicnet-stream",
  ".movie": "video/x-sgi-movie",
  ".mp2": "audio/mp2",
  ".mp3": "audio/mp3",
  ".mpa": "video/x-mpg",
  ".mpe": "video/x-mpeg",
  ".mpg": "video/mpg",
  ".mpp": "application/vnd.ms-project",
  ".mpt": "application/vnd.ms-project",
  ".mpv2": "video/mpeg",
  ".mpx": "application/vnd.ms-project",
  ".mxp": "application/x-mmxp",
  ".nrf": "application/x-nrf",
  ".odc": "text/x-ms-odc",
  ".p10": "application/pkcs10",
  ".p7b": "application/x-pkcs7-certificates",
  ".p7m": "application/pkcs7-mime",
  ".p7s": "application/pkcs7-signature",
  ".pci": "application/x-pci",
  ".pcx": "application/x-pcx",
  ".pdf": "application/pdf",
  ".pfx": "application/x-pkcs12",
  ".pic": "application/x-pic",
  ".pl": "application/x-perl",
  ".pls": "audio/scpls",
  ".png": "image/png",
  ".pot": "application/vnd.ms-powerpoint",
  ".ppm": "application/x-ppm",
  ".ppt": "application/vnd.ms-powerpoint",
  ".pr": "application/x-pr",
  ".prn": "application/x-prn",
  ".ps": "application/x-ps",
  ".ptn": "application/x-ptn",
  ".r3t": "text/vnd.rn-realtext3d",
  ".ram": "audio/x-pn-realaudio",
  ".rat": "application/rat-file",
  ".rec": "application/vnd.rn-recording",
  ".rgb": "application/x-rgb",
  ".rjt": "application/vnd.rn-realsystem-rjt",
  ".rle": "application/x-rle",
  ".rmf": "application/vnd.adobe.rmf",
  ".rmj": "application/vnd.rn-realsystem-rmj",
  ".rmp": "application/vnd.rn-rn_music_package",
  ".rmvb": "application/vnd.rn-realmedia-vbr",
  ".rnx": "application/vnd.rn-realplayer",
  ".rpm": "audio/x-pn-realaudio-plugin",
  ".rt": "text/vnd.rn-realtext",
  ".rtf": "application/x-rtf",
  ".sam": "application/x-sam",
  ".sdp": "application/sdp",
  ".sit": "application/x-stuffit",
  ".sld": "application/x-sld",
  ".smi": "application/smil",
  ".smk": "application/x-smk",
  ".sol": "text/plain",
  ".spc": "application/x-pkcs7-certificates",
  ".spp": "text/xml",
  ".sst": "application/vnd.ms-pki.certstore",
  ".stm": "text/html",
  ".svg": "text/xml",
  ".tdf": "application/x-tdf",
  ".tga": "application/x-tga",
  ".tif": "application/x-tif",
  ".tld": "text/xml",
  ".torrent": "application/x-bittorrent",
  ".txt": "text/plain",
  ".uls": "text/iuls",
  ".vda": "application/x-vda",
  ".vml": "text/xml",
  ".vsd": "application/vnd.visio",
  ".vss": "application/vnd.visio",
  ".vst": "application/x-vst",
  ".vsx": "application/vnd.visio",
  ".vxml": "text/xml",
  ".wax": "audio/x-ms-wax",
  ".wb2": "application/x-wb2",
  ".wbmp": "image/vnd.wap.wbmp",
  ".wk3": "application/x-wk3",
  ".wkq": "application/x-wkq",
  ".wm": "video/x-ms-wm",
  ".wmd": "application/x-ms-wmd",
  ".wml": "text/vnd.wap.wml",
  ".wmx": "video/x-ms-wmx",
  ".wp6": "application/x-wp6",
  ".wpg": "application/x-wpg",
  ".wq1": "application/x-wq1",
  ".wri": "application/x-wri",
  ".ws": "application/x-ws",
  ".wsc": "text/scriptlet",
  ".wvx": "video/x-ms-wvx",
  ".xdr": "text/xml",
  ".xfdf": "application/vnd.adobe.xfdf",
  ".xls": "application/vnd.ms-excel",
  ".xlw": "application/x-xlw",
  ".xpl": "audio/scpls",
  ".xql": "text/xml",
  ".xsd": "text/xml",
  ".xslt": "text/xml",
  ".x_b": "application/x-x_b",
  ".sisx": "application/vnd.symbian.install",
  ".ipa": "application/vnd.iphone",
  ".xap": "application/x-silverlight-app",
  ".zip": "application/x-zip-compressed",
}