do-web_message-flow.js

(() => {
  const DOMAIN_URL = 'https://brucke.auth0.com';
  const CLIENT_ID = 'wLSIP47wM39wKdDmOj6Zb5eSEw3JVhVp';

  const iframe = window.document.createElement('iframe');
  iframe.setAttribute('width', '0');
  iframe.setAttribute('height', '0');
  iframe.style.display = 'none';
  window.addEventListener(
    'message',
    async e => {
      if (e.origin !== DOMAIN_URL) return;
      let response = e.data.response;
      if (response.code) {
        const tokens = await fetch(`${DOMAIN_URL}/oauth/token`, {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json'
          },
          body: JSON.stringify({
            client_id: CLIENT_ID,
            code: response.code,
            grant_type: 'authorization_code',
            redirect_uri: window.location.origin
          })
        });
        response = await tokens.json();
      }
      alert(JSON.stringify(response, null, 2));
    },
    false
  );
  window.document.body.appendChild(iframe);
  iframe.setAttribute(
    'src',
    `${DOMAIN_URL}/authorize?client_id=${CLIENT_ID}&redirect_uri=${window.location.origin}&scope=openid%20profile%20email&response_type=code&response_mode=web_message&nonce=abc123&prompt=none`
  );
})();