Function onElement

src/injected/content/util.js:28–41

(tag, cb, arg)

 * @returns {Promise<void>}
 */
export const onElement = (tag, cb, arg) => new SafePromise(resolve => {
  if (elemByTag(tag)) {
    resolve(cb(arg));
  } else {
    const observer = new MutationObserver(() => {
      if (elemByTag(tag)) {
        observer.disconnect();
        resolve(cb(arg));
      }
    });
    // documentElement may be replaced so we'll observe the entire document
    observer.observe(document, { childList: true, subtree: true });
  }
});

export const makeElem = (tag, attrs) => {
  const el = document::createElementNS('http://www.w3.org/1999/xhtml', tag);