Function poll

testing/iframe.js:460–483

(description, condition, opt_onError, opt_timeout)

 * @template T
 */
export function poll(description, condition, opt_onError, opt_timeout) {
  return new Promise((resolve, reject) => {
    const start = Date.now();
    const end = opt_timeout || 1600;
    function poll() {
      const ret = condition();
      if (ret) {
        clearInterval(interval);
        resolve(ret);
      } else {
        if (Date.now() - start > end) {
          clearInterval(interval);
          if (opt_onError) {
            reject(opt_onError());
            return;
          }
          reject(new Error('Timeout waiting for ' + description));
        }
      }
    }
    const interval = setInterval(poll, 8);
    poll();
  });
}

/**
 * Polls for the given number of elements to have received layout or