getLoggedInEmail.js

async function getLoggedInEmail() {
  return new Promise((resolve, reject) => {
    try {
      // header element works on gmail
      // .ongoogle-material-minibar works on slides UI
      let header = document.querySelector('header');
      if (header === null) {
        // Try mini-bar
        header = document.querySelector('.onegoogle-material-minibar')
      }

      header
        .querySelectorAll('a[aria-label]')
        .forEach((el) => {
          let pattern = /Google Account:.*\n\((.*@.*)\)/
          let ariaLabel = el.getAttribute('aria-label'); 
          if (pattern.test(ariaLabel)) {
            const email = pattern.exec(ariaLabel)[1]
            // console.log(`Logged in email is : ${email}`);
            resolve(email);
          }
        });
      } catch (error) {
        reject(error);
      }
  });
}


getLoggedInEmail().then(email =>console.log(`Logged in email is : ${email}`));