This is a template prototype for the Facebook Pixel.

facebook_pixel.js

// Create Permissions
const copy = require('copyFromWindow');
const set = require('setInWindow');
const alias = require('aliasInWindow');
const queue = require('createQueue');
const call = require('callInWindow');
const map = require('makeTableMap');
const log = require('logToConsole');
const script = require('injectScript');

const initIds = copy('_fbq_gtm_ids') || [];
const pixelIds = data.pixelId;

// Utility function to use either fbq.queue[]
// (if the FB SDK hasn't loaded yet), or fbq.callMethod()
// if the SDK has loaded.
function getFbq() {
  // Return the existing 'fbq' global method if available
  let fbq = copy('fbq');
  if (fbq) {
    return fbq;
  }
  
  // Initialize the 'fbq' global method to either use
  // fbq.callMethod or fbq.queue)
  set('fbq', function() {    
    const callMethod = copy('fbq.callMethod.apply');
    if (callMethod) {           
      call('fbq.callMethod.apply', null, arguments); 
    } else {       
      call('fbq.queue.push', arguments);
    }
  });
  alias('_fbq', 'fbq');
  
  // Create the fbq.queue
  queue('fbq.queue');
    
  // Return the global 'fbq' method, created above
  return copy('fbq');
}

// Get reference to the global method
const fbq = getFbq();

// Build the fbq() command arguments
const props = data.propertyList ? map(data.propertyList, 'name', 'value') : {};
const command = data.eventName !== 'Custom' ? 'trackSingle' : 'trackSingleCustom';
const eventName = data.eventName !== 'Custom' ? data.eventName : data.customEventName;

// Handle multiple, comma-separated pixel IDs,
// and initialize each ID if not done already.
pixelIds.split(',').forEach(function(pixelId) {
  if (initIds.indexOf(pixelId) === -1) {

    // If the user has chosen to disable automatic configuration
    if (data.disableAutoConfig) {
      fbq('set', 'autoConfig', false, pixelId);
    }
    
    // Initialize pixel and store in global array
    fbq('init', pixelId);
    initIds.push(pixelId);
    set('_fbq_gtm_ids', initIds, true);
    
  }
  
  // Call the fbq() method with the parameters defined earlier
  fbq(command, pixelId, eventName, props);
});

// Log & Signal Success
const onSuccess = () => {
  log('Facebook script loaded successfully.');
  data.gtmOnSuccess();
};

// Log & Signal Failure
const onFailure = () => {
  log('Facebook script load failed.');
  data.gtmOnFailure();
};

script('https://connect.facebook.net/en_US/fbevents.js', onSuccess, onFailure, 'fbPixel');