How to authorize a site using fetch.js?

Question

Node.js

Good evening guys, I almost despaired of doing the right code, help someone please!
I removed the headers from the site and passed them to Headers, passed the parameters from form data to BOdy

utf8:✓
authenticity_token: token
login:[email protected]
password:1q2w3

Password and pass are not valid, here!
When it was valid, everything passed the rules, the status 200 OK gave out, but I did not believe that the authorization was successful with my code, and decided to make a non-valid log pass for verification, but inserting a non-valid received a completely identical answer, although the response in the browser when not valid is this here

{"error":"Неверное имя пользователя или пароль","fields":["login","password"]}

Here is my code:

const fetch = require('node-fetch');
var server = "http://сайт/login";

myHeaders = {
  Cookie: "КУКА",
  "Origin": "http://сайт",
  "Accept-Encoding": "gzip, deflate, br",
  "Accept-Language": "ru,en-US;q=0.8,en;q=0.6,zh;q=0.4,zh-TW;q=0.2,zh-CN;q=0.2",
  "User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
  "Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",
  "Accept": "application/json, text/javascript, */*; q=0.01",
  "Referer": "http://сайт/login",
  "X-Requested-With": "XMLHttpRequest",
  "Connection": "keep-alive"
};

var body = JSON.stringify({
      utf8: "✓",
      authenticity_token: "token",
      login: "[email protected]",
      password: "1e4r"
});

fetch(server, { method: 'POST', headers: myHeaders, body: body, credentials:'same-origin'})
   .then((res) => {
    console.log(res);
    console.log("___________________________________");
    console.log(res.headers);
  //return res.json();
})
  .catch(function(error) { console.log(error); });

and here is the console response

Response {
  size: 0,
  timeout: 0,
  [Symbol(Body internals)]:
   { body:
      Gunzip {
        _readableState: [ReadableState],

        readable: true,
        _events: [Object],
        _eventsCount: 7,
        _maxListeners: undefined,
        _writableState: [WritableState],
        writable: false,
        allowHalfOpen: true,
        _transformState: [Object],
        bytesRead: 0,
        _handle: [Zlib],
        _hadError: false,
        _writeState: [Uint32Array],
        _outBuffer: <Buffer 20 20 3c 64 69 76 20 63 6c 61 73 73 3d 22 6c 69 67 68 74 62 6f 78 5f 74 69 74 6c 65 22 3e 4c 6f 67 20 69 6e 3c 2f 64 69 76 3e 0a 0a 3c 64 69 76 20 73 ... >,
        _outOffset: 0,
        _level: -1,
        _strategy: 0,
        _chunkSize: 16384,
        _flushFlag: 2,
        _scheduledFlushFlag: 0,
        _origFlushFlag: 2,
        _finishFlushFlag: 2,
        _info: undefined },
     disturbed: false,
     error: null },
  [Symbol(Response internals)]:
   { url: 'https://ask.fm/login',
     status: 200,
     statusText: 'OK',
     headers: Headers { [Symbol(map)]: [Object] } } }
___________________________________
Headers {
  [Symbol(map)]:
   { 'content-type': [ 'text/html; charset=utf-8' ],
     'transfer-encoding': [ 'chunked' ],
     status: [ '200 OK' ],
     'cache-control': [ 'max-age=0, private, must-revalidate' ],
     etag: [ 'W/"1d0e1cbd9e4830bb83328d62a5cbd13a"' ],
     'x-frame-options': [ 'SAMEORIGIN' ],
     'x-xss-protection': [ '1; mode=block' ],
     'x-content-type-options': [ 'nosniff' ],
     date: [ 'Wed, 06 Jun 2018 19:50:27 GMT' ],
     'set-cookie':
      [ 'locale=en; path=/; expires=Fri, 07 Jun 2019 01:50:27 -0000',
        '_m_ask_fm_session=OUR1V3RDMloreEJYTTg4dDJqVDFYL01yZVhkbzJVRDFzZEtYTFozZXM4N2hpaXVZRXIyUFE3NndoNkVHc25uU0ovZy9nRHUyWU9nZEZXc2xNZHI2OXRNL1dwb0hNVFhGNjhWUTh1NE9LSXdmREc3M25JaWl1ZnhNSVBlSDJoY1dZMVVqTDdCWm9UQ1ptWW9CanRYYmlBPT0tLStWTHRCUzl1Ym
VDaGJvS3RvWEVtVmc9PQ%3D%3D--9f2790322cdd7f2da9f04f5a5984f94b17d76ca5; path=/; expires=Sat, 09 Jun 2018 19:50:27 -0000; secure; HttpOnly' ],
     server: [ 'Ask.FM Web Service' ],
     'content-encoding': [ 'gzip' ],
     'strict-transport-security': [ 'max-age=63072000' ] } }

What am I doing wrong?