how to get the request body and correct header of FormData in axios adapter

[fancy45daddy]

Describe the issue

import axios from 'axios'

async function my(config)
{
    console.log(config)
}

const axios = axios.create({validateStatus:false, adapter:my})
console.log(await axios.postForm('https://httpbin.org/post', {1:2,buf:new Buffer.from('aaa')}).then(_ => _.data))

the output is:

FormData {
  _overheadLength: 200,
  _valueLength: 2,
  _valuesToMeasure: [],
  writable: false,
  readable: true,
  dataSize: 0,
  maxDataSize: 2097152,
  pauseStreams: true,
  _released: false,
  _streams: [
    '----------------------------441912445856199199041598\r\n' +
      'Content-Disposition: form-data; name="1"\r\n' +
      '\r\n',
    '2',
    [Function: bound ],
    '----------------------------441912445856199199041598\r\n' +
      'Content-Disposition: form-data; name="buf"\r\n' +
      'Content-Type: application/octet-stream\r\n' +
      '\r\n',
      <Buffer 61 61 61>,
    [Function: bound ]
  ],
  _currentStream: null,
  _insideLoop: false,
  _pendingNext: false,
  _boundary: '--------------------------441912445856199199041598'
}

and

headers: Object [AxiosHeaders] {
    Accept: 'application/json, text/plain, */*',
    'Content-Type': 'multipart/form-data'
  },

I want to know how to construct the correct request body

----------------------------441912445856199199041598
Content-Disposition: form-data; name="1"

2
----------------------------441912445856199199041598
Content-Disposition: form-data; name="buf"
Content-Type: application/octet-stream

aaa
----------------------------441912445856199199041598--

and the correct content-type

'Content-Type': 'multipart/form-data; boundary=----------------------------441912445856199199041598'

I see there similar code in https://github.com/axios/axios/blob/main/lib/adapters/http.js. But I have no idea how to reuse the source code in https://github.com/axios/axios/blob/main/lib/adapters/http.js.

Example Code

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Expected behavior

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Axios Version

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Adapter Version

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Browser

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Browser Version

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OS

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Additional context/Screenshots

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