How I add GA to my Ember apps.

initializer.js

# app/instance-initializers/google-analytics.js

import ENV from "./config/environment";

export function initialize(application) {
  let fastboot = application.lookup('service:fastboot');
  window.dataLayer = window.dataLayer || [];

  if (!fastboot.get('isFastBoot')) {
    let body = document.getElementsByTagName('body').item(0);
    let analyticsScript = document.createElement('script');
    analyticsScript.setAttribute('type', 'text/javascript');
    analyticsScript.setAttribute('async', '');
    analyticsScript.setAttribute('src', `https://www.googletagmanager.com/gtag/js?id=${ENV.googleAnalyticsTrackingId}`);
    body.appendChild(analyticsScript);

    window.dataLayer.push(['js', new Date()]);
    window.dataLayer.push(['config', ENV.googleAnalyticsTrackingId]);
  }
}

export default {
  name: 'google-analytics',
  initialize
};

router.js

# app/router.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';
import { on } from '@ember/object/evented';
import { inject as service } from "@ember/service";

const Router = EmberRouter.extend({
  googleAnalytics: service('google-analytics'),
  location: config.locationType,
  rootURL: config.rootURL,
  sendAnalytics: on('didTransition', function() {
    this.googleAnalytics.gtag('config', config.googleAnalyticsTrackingId, { page_path: this.url });
  })
});

Router.map(function() {});

export default Router;

service.js

# app/services/google-analytics.js

import Service from '@ember/service';

export default Service.extend({
  gtag() {
    window.dataLayer.push(arguments);
  }
});