Implementing Twitter's OAuth with only request

apiTwitter.js

import request from 'request-promise'
import {parse as qsparse} from 'querystring'
import parse from 'co-body'

var post = request.defaults({json: true}).post
const TWITTER_KEY = ''
const TWITTER_SECRET = ''
const TWITTER_CALLBACK_URL = ''

export function * requestToken () {
  var body = yield post({
    uri: 'https://api.twitter.com/oauth/request_token',
    oauth: {
      consumer_key: TWITTER_KEY,
      consumer_secret: TWITTER_SECRET,
      callback: TWITTER_CALLBACK_URL
    }
  })
  var data = qsparse(body)
  this.body = {
    requestToken: data.oauth_token,
    requestTokenSecret: data.oauth_token_secret
  }
}

export function * login () {
  const body = yield parse(this)
  this.assert(body.requestToken, 400, 'Require param missing: `request token`')
  this.assert(body.verifier, 400, 'Required param missing `verifier`')
  
  var accessTokenRequest = yield post({
    uri: 'https://api.twitter.com/oauth/access_token',
    oauth: {
      consumer_key: TWITTER_KEY,
      consumer_secret: TWITTER_SECRET,
      token: body.requestToken,
      verifier: body.verifier
    }
  })
  var userData = qsparse(accessTokenRequest)
  /*
  userData = {
    user_id,
    screen_name,
    oauth_token,
    oauth_token_secret
  }
  */
  
  // store info on the user here
  
  this.body = userData
}

export function * twitterPost () {
  var body = yield parse(this)
  this.assert(body.message, 400, 'Required field message not found')
  
  // assume user has oauth_token and oauth_token_secret stored.
  
  yield post({
    uri: 'https://api.twitter.com/1.1/statuses/update.json',
    qs : {
      status : body.message
    },
    oauth: {
      consumer_key: TWITTER_KEY,
      consumer_secret: TWITTER_SECRET,
      token : user.oauth_token,
      token_secret : user.oauth_token_secret
    }
  })
}

client.js

import {parse} from 'query-string'

var qs = parse(document.location.search)
if (qs.oauth_token && qs.oauth_verifier) {
  var [requestToken, verifier] = [qs.oauth_token, qs.oauth_verifier]
  fetch(LOGIN_URL, {
    method: 'POST',
    body: JSON.stringify({requestToken, verifier})
  })
  .then((res) => res.json())
  .then((data) => console.log(data))
}

function twitterLogin () {
  fetch(REQUEST_TOKEN_URL, {
    method: 'POST'
  })
  .then(res => res.json())
  .then((body) => {
    document.location.href = `https://api.twitter.com/oauth/authenticate?oauth_token=${body.requestToken}`
  })
}