GET GA4 client id

get_ga4_client_id.js

// Constant for Measurement ID without G-
const MEASUREMENT_ID = 'G-DKNEXDCMS2';
// Function to read cookies
function get_ga_clientid_from_cookies() {
    var cookie = {};
    document.cookie.split(';').forEach(function(el) {
      var splitCookie = el.split('=');
      var key = splitCookie[0].trim();
      var value = splitCookie[1];
      cookie[key] = value;
    });
  return cookie["_ga"].substring(6);
  }

// Function to get GA4 client ID
function getGA4ClientID() {
  // Check if gtag is defined
  if (typeof gtag === 'function') {
    return new Promise((resolve, reject) => {
      console.log('Using gtag API to get client ID');
      gtag('get', `${MEASUREMENT_ID}`, 'client_id', (clientID) => {
        if (clientID) {
          console.log('Client ID from gtag API:', clientID);
          resolve(clientID);
        } else {
          console.log('Failed to get client ID from gtag API');
          reject('Failed to get client ID from gtag API');
        }
      });
    });
  } else {
    // Fallback to reading cookies if gtag is not defined
    console.log('gtag is not defined, falling back to reading cookies');
      const clientID =  get_ga_clientid_from_cookies();
      if (clientID) {
        console.log('Client ID from cookies:', clientID);
        return Promise.resolve(clientID);
      } else {
        console.log('Failed to extract client ID from cookies');
        return Promise.reject('Failed to extract client ID from cookies');
      }
 
  }
}

// Example usage
getGA4ClientID()
  .then((clientID) => {
    // Do something with the client ID
    console.log(clientID);
  })
  .catch((error) => {
    console.error(error);
  });