Function getAmpConfig

tools/experiments/experiments.js:379–405

* Loads the AMP_CONFIG objects from whatever the v0.js is that the user has * (depends on whether they opted into one of the pre-release channels or into a * specific RTV) so that experiment state can reflect the default activated * experiments. * @return {Promise } the active AMP_CONFIG, p

()

 * @return {Promise<JSON>} the active AMP_CONFIG, parsed as a JSON object
 */
function getAmpConfig() {
  const deferred = new Deferred();
  const {promise, reject, resolve} = deferred;
  const xhr = new XMLHttpRequest();
  xhr.addEventListener('load', () => {
    resolve(xhr.responseText);
  });
  xhr.addEventListener('error', () => {
    reject(new Error(xhr.statusText));
  });
  // Cache bust, so we immediately reflect cookie changes.
  xhr.open('GET', '/v0.js?' + Math.random(), true);
  xhr.send(null);
  return promise
    .then((text) => {
      const match = text.match(/self\.AMP_CONFIG=(\{.+?\})/);
      if (!match) {
        throw new Error("Can't find AMP_CONFIG in: " + text);
      }
      // Setting global var to make standard experiment code just work.
      return (self.AMP_CONFIG = JSON.parse(match[1]));
    })
    .catch((error) => {
      console./*OK*/ error('Error fetching AMP_CONFIG', error);
      return {};
    });
}

// Start up.
getAmpConfig().then(() => {