Long polling implementation in Js

polling.js

const axios = require('axios').default;

function getAPIClient() {
  const axiosConfig = {
    baseURL: 'https://csrng.net/csrng/csrng.php',
    timeout: 5000,
  };

  return axios.create(axiosConfig);
}

function getData() {
  const client = getAPIClient();
  return client.get('/?min=0&max=100');
}

// create a promise that resolves after a short delay
function delayPromise(ms) {
  return new Promise(function(resolve) {
    setTimeout(resolve, ms);
  });
}

// cb is the callback function
// interval is how often to poll
// timeout is how long to poll waiting for a result (0 means try forever)
function poll(cb, predicate, errorHandler, interval, timeout) {
  let start = Date.now();

  function run() {
    return cb().then(function({ data }) {
      console.log('data:', data);
      if (predicate(data)) {
        // we know we're done here, return from here whatever you
        // want the final resolved value of the promise to be
        return data;
      } else {
        if (timeout !== 0 && Date.now() - start > timeout) {
          errorHandler();
        } else {
          // run again with a short delay
          return delayPromise(interval).then(run);
        }
      }
    });
  }
  return run();
}

function isGreaterThan90([number]) {
  return number.random > 90;
}

function errorHandler() {
  throw new Error('timeout error on poll');
}

function logResult(data) {
  data = JSON.stringify(data, null, 2);
  console.log(`result: ${data}`);
}

poll(getData, isGreaterThan90, errorHandler, 1000, 30 * 1000)
  .then(logResult)
  .catch(console.error);