Function fetchDocument

examples/pwa/pwa.js:373–404

* @param {string} url * @return {!Promise<!Document>}

(url)

 * @return {!Promise<!Document>}
 */
function fetchDocument(url) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.responseType = 'document';
    xhr.setRequestHeader('Accept', 'text/html');
    xhr.onreadystatechange = () => {
      if (xhr.readyState < /* STATUS_RECEIVED */ 2) {
        return;
      }
      if (xhr.status < 100 || xhr.status > 599) {
        xhr.onreadystatechange = null;
        reject(new Error(`Unknown HTTP status ${xhr.status}`));
        return;
      }
      if (xhr.readyState == /* COMPLETE */ 4) {
        if (xhr.responseXML) {
          resolve(xhr.responseXML);
        } else {
          reject(new Error(`No xhr.responseXML`));
        }
      }
    };
    xhr.onerror = () => {
      reject(new Error('Network failure'));
    };
    xhr.onabort = () => {
      reject(new Error('Request aborted'));
    };
    xhr.send();
  });
}

/**
 * @param {string} url