node fetch get extract hash post

get_extract_hash_post.js

// grab page - extract text - send post request back to same page
const crypto = require('crypto');
const http = require('http');
const querystring = require('querystring');
const host = 'someapp.host';
const port = 38008;
const path = '/';
const options = { host, port, path };
let Cookie;

new Promise((resolve, reject) => {
  const req = http.request(Object.assign(options, { method: 'GET' }), res => {
    Cookie = res.headers['set-cookie'];
    const data = [];
    res.on('data', d => data.push(d));
    res.on('end', () => resolve(Buffer.concat(data).toString()));
  });
  req.on('error', reject);
  req.end();
})
.then(d => {
  const token = /.*center'>([^<]+)<.*/g.exec(d)[1];
  const hash = crypto.createHash('md5').update(token).digest('hex');
  return new Promise((resolve, reject) => {
    const postData = querystring.stringify({hash});
    const headers = {
      Cookie,
      'Content-Type': 'application/x-www-form-urlencoded',
      'Content-Length': Buffer.byteLength(postData),
    };
    const req = http.request(Object.assign(options, { method: 'POST', headers }), res => {
      const data = [];
      res.on('data', d => data.push(d));
      res.on('end', () => resolve(Buffer.concat(data).toString()));
    });
    req.on('error', reject);
    req.write(postData);
    req.end();
  });
})
.then(console.log, console.log);