A simple way to poll for something in JS.

poll.js

/**
 * @typedef poll__options
 * @property {((criteriaResult: any) => void)=} callback
 *    Optional.  If not specified then `poll` returns a promise that will resolve once `criteria` returns a `true`-ish value.
 * @property {number} [timeout=50]
 *    Optional.  Number of milliseconds between one call to criteria and the next (excluding the initial which is immediate).  Defaults to `50`.
 * @property {boolean} [ignoreErrors=false]
 *   Optional.  Whether or not an error coming from `criteria` will be ignored.  Defaults to `false`.
 */
/**
 * @param {() => any} criteria
 *    Function that is run every timeout period to determine whether the polling can stop.
 * @param {poll__options=} options
 */
function poll(criteria, options) {
  const {callback, timeout, ignoreErrors} = options ?? {};

  function attempt(resolve) {
    let result;
    try {
      result = criteria();
    }
    catch (err) {
      if (!ignoreErrors) throw err;
    }
    if (result) {
      resolve(result);
    }
    else {
      setTimeout(() => attempt(resolve), timeout ?? 50);
    }
  }

  if (callback) {
    attempt(callback);
  }
  else {
    return new Promise(resolve => void attempt(resolve));
  }
}