Function invoke

src/impression.js:219–234

* Send the url to ad server and wait for its response * @param {!Window} win * @param {string} clickUrl * @return {!Promise<?JsonObject>}

(win, clickUrl)

 * @return {!Promise<?JsonObject>}
 */
function invoke(win, clickUrl) {
  if (getMode().localDev && !getMode().test) {
    clickUrl = 'http://localhost:8000/impression-proxy?url=' + clickUrl;
  }
  return Services.xhrFor(win)
    .fetchJson(clickUrl, {
      credentials: 'include',
    })
    .then((res) => {
      // Treat 204 no content response specially
      if (res.status == 204) {
        return null;
      }
      return res.json();
    });
}

/**
 * parse the response back from ad server