This is an express proxy middleware. In addition to normal proxy forwarding function, it can also extend additional parameters, such as extending headers, extending URL parameters, and extending body parameters

install

npm i express-create-proxy

usage

const express = require('express')
const app = express()
const path = require('path')
const bodyParser = require('body-parser')
const { createProxy } = require('express-create-proxy')
const proxy = createProxy({
  proxy: {
    '^/api': {
      target: 'http://localhost:3002',
      pathRewrite: { // rewrite url reference to http-proxy-middleware
        '^/api': '/api'
      }
    }
  }
})
app.use(proxy)
app.listen(3000, () => {
  console.log('start at 3000')
})

proxy config

const proxy = createProxy({
  proxy: {
    '^/api': {
      target: 'http://localhost:3002',
      pathRewrite: { // rewrite url reference to http-proxy-middleware
        '^/api': '/api'
      }
    },
    '^/another': {
      target: 'http://xxxx.com'
    }
  }
})
// or proxy all
const proxy = createProxy({
  proxy: 'http://localhost:3002'
})

requestOptions (addtional params data headers for every request)

const proxy = createProxy({
  proxy: {
    '^/api': {
      target: 'http://localhost:3002',
      pathRewrite: {
        '^/api': '/api'
      }
    }
  },
  requestOptions: {
    params: { // url search
      a: 'a'
    },
    data: { // body data
      b: 'b',
      c: 'c',
      file: { // post file (only when content-type: multipart/form-data)
        path: 'xxxx.jpg'
      }
    },
    headers: { // header
      'someHeader': 'headerValue'
    },
    beforeRequest(req, res, options) {
      // options is equal to requestOptions 
      console.log(options)
      return {
        params: {
          // some url params
          ...(options.params || {})
        },
        data: {
          // some body data
          ...(options.data || {})
        },
        headers: {
          // some headers
          ...(options.headers || {})
        }
      }
    },
    onRequest (url, httpOptions, httpReq, req, res) { // when send http request
      console.log(url) // request url
      console.log(httpOptions) // request options
    },
    onResponse (httpRes, httpReq, res, req) { // http.ServerResponse, http.ClientRequest
    },
  }
})

modules

1. proxyRequest (req, res, url, options)

usage

const { proxyRequest } = require('express-create-proxy')
app.get('/api/test', (req, res) => {
  const target = 'http://localhost:3002'
  proxyRequest(req, res, target + req.originalUrl, {
    params: {}, // aditional params
    data: {}, // aditional data
    headers: {}, // aditional headers
    redirect: false, // is redirection supported
    beforeRequest(req, res, options) {
      return options
    },
    onResponse (httpRes, httpReq) { // http.ServerResponse, http.ClientRequest
    },
  })
})

// redirect
const { proxyRequest } = require('express-create-proxy')
app.get('/api/test', (req, res) => {
  const target = 'http://localhost:3002'
  proxyRequest(req, res, target + req.originalUrl, {
    params: {}, // aditional params
    data: {}, // aditional data
    headers: {}, // aditional headers
    redirect: true // is redirection supported
  })
})

// custom responseData
const { proxyRequest } = require('express-create-proxy')
app.get('/api/json', (req, res) => {
  const target = 'http://localhost:3002'
  function responseCallback (resData) {
    const data = {
      ...resData,
      name: 'jack'
    }
    res.send(data)
  }
  proxyRequest(req, res, target + req.originalUrl, {
    params: {}, // aditional params
    data: {}, // aditional data
    headers: {}, // aditional headers
    redirect: true, // is redirection supported
  }, responseCallback)
})


// stream download
const { proxyRequest } = require('express-create-proxy')
app.get('/api/download', (req, res) => {
  const target = 'http://localhost:3002'
  function responseCallback (resStream) {
    res.set('Content-Disposition', 'attachment; filename="download.jpg"')
    res.set('Content-Type', 'image/jpeg')
    resStream.pipe(res)
  }
  proxyRequest(req, res, target + req.originalUrl, {
    params: {}, // aditional params
    data: {}, // aditional data
    headers: {}, // aditional headers
    redirect: true, // is redirection supported
    responseType: 'stream'
  }, responseCallback)
})

2. File

properties

1. type: file's MIME type
2. path: file's absolute path
3. size: file size
4. source: file stream (fs.createReadStream(file.path))
5. filename: file's name defaults path.basename(file.path)

usage

const { proxyRequest, File } = require('express-create-proxy')
// req.get('content-type')  must be multipart/form-data
// basic usage
app.post('/api/test', (req, res) => {
  proxyRequest(req, res, req.baseUrl + req.url, {
    params: {},
    data: {
      file: {
        path: 'xxxx.jpg',
        filename: 'xxx.jpg'  // default value is require('path').basename(file.path),
        type: 'image/jpeg' // default require('mime-types').lookup(file.path)
      }
    },
    headers: {},
    // beforeRequest(req, res, options) {
    //   return options
    // }
  })
})

// advanced usage
app.post('/api/test', (req, res) => {
  proxyRequest(req, res, req.baseUrl + req.url, {
    params: {},
    data: {
      file: new File('xxx.jpg', {
        filename: 'xxx.jpg'  // default value is require('path').basename(file.path),
        type: 'image/jpeg' // default require('mime-types').lookup(file.path)
      })
    },
    headers: {},
    // beforeRequest(req, res, options) {
    //   return options
    // }
  })
})

3. FormData

properties

1. form: instance of CombinedStream reference to combined-stream
2. boundary: multipart/form-data boundary defaults uuidv4()

methods

1. getContentType: return multipart/form-data; boundary=${this.boundary}
2. getContentLength: get form data's bytelength
3. setBoundary(boundary: String): set boundary
4. append(key, value): append data
5. build(data: Object): build form Data

const { FormData, File } = require('express-create-proxy')
const formData = new FormData()
formData.build({
  data1: 'data1',
  data2: 'data2',
  file: new File('xxxx.jpg'),
  file1: {
    path: 'xxxx.jpg'
  }
})
// build equal to 
// const data = {
//   data1: 'data1',
//   data2: 'data2',
//   file: new File('xxxx.jpg'),
//   file1: {
//     path: 'xxxx.jpg'
//   }
// }
// Object.keys(data).forEach(key => {
//   formData.append(key, data[key])
// })

6. pipe(src: writeStream, Duplex Transform, options: Object({hasTail: true | false}))

usage

const { FormData, request, File } = require('express-create-proxy')
const formData = new FormData()
// formData.setBoundary('xxxxxx')  // set boundary defaults uuidv4()
formData.append('key', 'value')
formData.append('file1', new File(path.resolve(__dirname, '../test.txt')))
const httpReq = request('http://localhost:3003/file', {
  method: 'post',
  params: {},
  headers: { // set header  or use node clientRequest api httpReq.setHeader('content-type', formData.getContentType())
    'content-type': formData.getContentType(),
  }
})
httpReq.on('response', res => {
  console.log(res.statusCode)
})
httpReq.on('error', e => {
  console.log(e)
})
formData.pipe(httpReq, {hasTail: true}, () => { // if hasTail: false  There is no ending separator (source code is `--${this.boundary}--\r\n`) defaults true
  httpReq.setHeader('content-length', formData.getContentLength())
})