User Tracker - Roughly follows the Google Analytics tracker implementation

user-tracker.js

import { pick } from 'lodash';
import Cookies from 'js-cookie';
import queryString from 'query-string';

const utmParams = [
    'utm_source',
    'utm_medium',
    'utm_campaign',
    'utm_term',
    'utm_content',
];

// Only set once when at start of session
if (!Cookies.get('userTracker')) {

    const userTracker = {};

    // convert query string to object
    const searchParams = queryString.parse(location.search);

    // Only pull valid UTM params not all query params
    const campaignParams = pick(searchParams, utmParams);

    // Test for missing utm_source or utm_medium
    const noSourceOrMedium = (!campaignParams.utm_source || !campaignParams.utm_medium);

    // Test for organic search referral
    const searchReferral = document.referrer.match(/https?:\/\/(.*)\.(google|bing|yahoo)\.([^/?]*)/);

    // Sensible defaults for missing utm_source or utm_medium
    if (noSourceOrMedium) {

        if (searchParams.gclid) {
            campaignParams.utm_source = 'google';
            campaignParams.utm_medium = 'cpc';
        } else if (searchReferral) {
            campaignParams.utm_source = searchReferral[2];
            campaignParams.utm_medium = 'organic';
        } else if (document.referrer) {
            campaignParams.utm_source = document.referrer;
            campaignParams.utm_medium = 'referral';
        }

        campaignParams.utm_source = 'direct';
        campaignParams.utm_medium = 'none';
    }

    // Store as a property in case we want additional data in userTracker
    userTracker.campaignParams = campaignParams;

    // Store userTracker as cookie for duration of session
    Cookies.set('userTracker', userTracker, {
        secure: true,
    });
}