https://www.gap.at/gtm-init.js

1(function initGtm() {
2    var gtmMeta = document.querySelector('meta[name="gtm-id"]');
3    var gtmId = gtmMeta ? gtmMeta.getAttribute("content") : "";
4
5    if (!gtmId || !gtmId.trim()) {
6        return;
7    }
8
9    var dataLayer = (window.dataLayer = window.dataLayer || []);
10
11    dataLayer.push({
12        event: "dataLayerInit",
13        originalLocation:
14            document.location.protocol +
15            "//" +
16            document.location.hostname +
17            document.location.pathname +
18            document.location.search,
19    });
20
21    window.dataLayer = window.dataLayer || [];
22    window.dataLayer.push({
23        "gtm.start": new Date().getTime(),
24        event: "gtm.js",
25    });
26
27    var firstScript = document.getElementsByTagName("script")[0];
28    var gtmScript = document.createElement("script");
29
30    gtmScript.async = true;
31    gtmScript.src =
32        "https://www.googletagmanager.com/gtm.js?id=" +
33        encodeURIComponent(gtmId);
34
35    if (firstScript && firstScript.parentNode) {
36        firstScript.parentNode.insertBefore(gtmScript, firstScript);
37        return;
38    }
39
40    document.head.appendChild(gtmScript);
41})();