gistfile1.js

const jwt_simple = require('jwt-simple');
const fetch = require('node-fetch');
const qs = require('query-string');

const JWT_BEARER_URI = 'urn:ietf:params:oauth:grant-type:jwt-bearer';
const WELKIN_ENDPOINT_URL = 'https://api.welkinhealth.com/v1/token';


async function getToken() {
  const tokenData = {
    'iss': CLIENT_ID,
    'aud': WELKIN_ENDPOINT_URL,
    'exp': Math.round(new Date() / 1000) + 3600,
    'scope': 'all',
  };
  const token = jwt_simple.encode(tokenData, CLIENT_SECRET, 'HS256');
  const res = await fetch(WELKIN_ENDPOINT_URL, {
    method: 'POST',
    body: qs.stringify({
      assertion: token,
      grant_type: JWT_BEARER_URI,
    }),
  });

  const j = await res.json();
  console.log(j);
}

getToken().then(() => console.log('done'));