node做中间层如何进行文件上传

node做中间层如何进行文件上传
如今越来越多的前端项目加入了node做中间层， 进行一些请求的拦截，转发等，但是在进行ajax进行文件上传的时候比如无法直接获取客户端传递过来的formdata数据。node层请求库我使用的是node-fetch。

需要安装以下库：
npm install --save node-fetch // node层请求库
npm install --save form-data
npm install --saveconnect-multiparty // 文件上传解析

代码部分
```路由部分

```css
    import asyncRouter from '../helpers/asyncRouter'
const router = asyncRouter();
import multipart from 'connect-multiparty'
const multipartMiddleware = multipart()
const fillPath = require('path')
module.exports = (app) => {
    app.use('/app-live', router);
};
router.all('/*', multipartMiddleware,async(req, res, next) => {
    let path = req._parsedUrl.path,
        method = req.method,
        args = method === 'POST' ? req.body : req.query; 
        let responseData = {}
        if (req.headers['content-type'] && req.headers['content-type'].includes('multipart/form-data')){
          responseData = await req.api(path, method, { body:req.files.file })
        } else if ( req.path === '/download'){
          path = req.path 
          responseData = await req.api(path, method, { body: args})
        } else {
          console.log(path);
           responseData = await req.api(path, method, { body: args});
        }
    responseData.ServerDate = new Date().getTime();
    return res.json(responseData);
});  

```handlebars
import fetch from 'node-fetch' // 网络请求库
import settings from '../config'; // 获取请求baseUrl路径
import fs from 'fs'
import path from 'path'
import FormData from 'form-data' // 文件上传formData对象
async function request(opts, {}) {
    const method = opts.method || 'GET';
    opts.headers = opts.headers || {};
    opts.headers.Authorization = opts.headers.Authorization;
    if (!_.has(opts.headers, 'Content-Type')) {
        opts.headers['Content-Type'] = 'application/json';
    }
    const body = opts.body || {};
    if (!body.Token) {
        body.Token = opts.token;
    }
    // 普通请求
    const requestOptions = function() {
        const header = Object.assign({},opts.headers)
        return  new Promise(async (resolve, reject) => {
          // post请求配置
          const optionsPost = {
            timeout: 100000,
            headers: header,
            method,
            body: method === "POST" ? JSON.stringify(body) : {},
          }
          // get强求配置
          const optionsGet = {
            timeout: 100000,
            headers: header,
            method
          }
          resolve( method === "POST" ? optionsPost: optionsGet )
        })
    };
    
    // 文件上传
    const requestFormDataOptions = function() {
    const {path:filePath, originalFilename } = body 
    const newPath = path.join(path.dirname(filePath), originalFilename)
    const header = Object.assign({},opts.headers)
    delete header['Content-Type'] // node-fetach 上传文件不需要请求Content-Type
    return  new Promise((resolve, reject) => {
      fs.rename(filePath, newPath, async function (err) {
        if(err) return
        const file = fs.createReadStream(newPath)
        const form = new FormData()
        form.append('file', file)
        resolve({
          timeout: 100000,
          headers:header,
          method,
          body: form 
        })
      })
    })
  };
  
  // 获取配置参数
  async function getOptions() {
    return  opts.headers['Content-Type'].indexOf('multipart/form-data') === -1 ? await requestOptions() : await requestFormDataOptions()
  }
  try {
          // 普通请求
          const reqTimeCurrent = new Date()
          const response =  await fetch(settings.BASE_URL + opts.path, await getOptions())
          if (response.status === 204) {
              return { deleted: true, url: settings.BASE_URL + opts.path};
          }
          const responseCopy = response
          return {
            requestUrl: settings.BASE_URL + opts.path,
            requestParams: body,
            ...await response.json()
          }
    } catch (err) {
        return {
          requestUrl: settings.BASE_URL + opts.path,
          requestParams: body,
          ...err
        }
        
    }
}