Amplitude-GTM-cross-domain.html

<script>
    (function () {
    console.log("Entering Custom HTML Tag Script v8");
        var timeout = 10000; // 1000000ms = 10 seconds

        // This is the promise code, so this is the useful bit
        function ensureUserIsSet(timeout) {
            var start = Date.now();
            return new Promise(waitForUser); // set the promise object within the ensureUserIsSet object

            // waitForUser makes the decision whether the condition is met
            // or not met or the timeout has been exceeded which means
            // this promise will be rejected
            function waitForUser(resolve, reject) {
                console.log("Waiting for user");
                if (typeof amplitudeGTM !== 'undefined' && typeof amplitudeGTM.getDeviceId() !== "undefined") {
                    console.log("Resolving with deviceID " + window.amplitudeGTM.getDeviceId());
                    resolve(amplitudeGTM.getDeviceId());
                } else if (timeout && (Date.now() - start) >= timeout) {
                    console.log("Rejecting");
                    reject(new Error("timeout"));
                } else {
                    console.log("Resetting timeout");
                    setTimeout(waitForUser.bind(this, resolve, reject), 30);
                }
            }
        }

        // This runs the promise code
        ensureUserIsSet(timeout).then(function () {
            console.log("Getting ready to decorate");
            var domainsToDecorate = [
                'foo.com', 'anotherdomain.com' //add or remove domains (without https or trailing slash)
            ],
                queryParams = [
                    'utm_campaign', //add or remove query parameters you want to transfer
                    'utm_source',
                    'utm_medium',
                ]
            // do not edit anything below this line
            var links = document.querySelectorAll('a');
            // check if links contain domain from the domainsToDecorate array and then decorates
            for (var linkIndex = 0; linkIndex < links.length; linkIndex++) {
                console.log("Checking " + links[linkIndex] + " for decoration.");
                for (var domainIndex = 0; domainIndex < domainsToDecorate.length; domainIndex++) {
                    if (links[linkIndex].href.indexOf(domainsToDecorate[domainIndex]) > -1 && links[linkIndex].href.indexOf("#") === -1) {
                        links[linkIndex].href = decorateUrl(links[linkIndex].href);
                    }
                }
            }
            // decorates the URL with query params
            function decorateUrl(urlToDecorate) {
                console.log("Decorating URL " + urlToDecorate);
                urlToDecorate = (urlToDecorate.indexOf('?') === -1) ? urlToDecorate + '?' : urlToDecorate + '&';
                var collectedQueryParams = [];
                for (var queryIndex = 0; queryIndex < queryParams.length; queryIndex++) {
                    if (getQueryParam(queryParams[queryIndex])) {
                        collectedQueryParams.push(queryParams[queryIndex] + '=' + getQueryParam(queryParams[queryIndex]))
                    }
                }
                var ampDeviceId = amplitudeGTM.getDeviceId();
                console.log("Amplitude Device ID= " + ampDeviceId);
                collectedQueryParams.push('deviceId=' + ampDeviceId);
                return urlToDecorate + collectedQueryParams.join('&');
            }
            // borrowed from https://stackoverflow.com/questions/831030/
            // a function that retrieves the value of a query parameter
            function getQueryParam(name) {
                if (name = (new RegExp('[?&]' + encodeURIComponent(name) + '=([^&]*)')).exec(window.location.search))
                    return decodeURIComponent(name[1]);
            }
        });
    console.log("Exiting Custom HTML Tag Script");
    })();
</script>