getRootDomain! — GTM Variable Template for GTM

VARIABLES › GTM

getRootDomain! EXTENDED GTM

Direct (.tpl) Apply (.tpl)

Determines the root domain of the current page by testing cookie access at each domain level. The result is cached for performance.

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GTM Configuration

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Read-only Preview

getRootDomain!

This function takes no parameters.

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the root domain before returning it (e.g., d => '.' + d to add leading dot for cookies, d => d.toUpperCase()). Useful for formatting.

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Related Variables

Same category: GTM

→ document.title → estimateReadingTime → gaEcommerceEventList → gaLeadGenerationEventList → getCookieValue → getDataLayerByEvent → getDataLayerCurrent → getDataLayerValue → getGaMeasurementIds → getLocalStorage → gtmIsDebugMode → gtmIsPreviewMode → hasLocalStorageKey → isGrantedAdPersonalization → isGrantedAdStorage → isGrantedAdUserData → isGrantedAnalyticsStorage → isGrantedFunctionalityStorage → isGrantedPersonalizationStorage → isGrantedSecurityStorage → 𝐀𝐑𝐑𝐀𝐘 From Indexed Values Generator - Array → 𝐀𝐑𝐑𝐀𝐘 From Values Generator - Array → 𝐂𝐎𝐌𝐌𝐀𝐍𝐃 𝐓𝐀𝐁𝐋𝐄 Lazy Generator (Advanced) - Object → 𝐎𝐁𝐉𝐄𝐂𝐓 From Arrays Generator - Object → 𝐎𝐁𝐉𝐄𝐂𝐓 Smart Generator - Object → 𝐎𝐁𝐉𝐄𝐂𝐓 Transformer Generator (Advanced) - Object

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Under the Hood

📜 View Implementation Code

/**
 * Determines the root domain of the current hostname by attempting to set a test cookie at each level.
 * Uses templateStorage to cache the result for performance.
 *
 * @param {Function|string} [data.out] - Optional output handler: function to transform result or string with format.
 * 
 * @returns {string} The root domain where cookies can be set (e.g., "example.com").
 *
 * @author David Vallejo
 * @see https://bit.ly/4jXILvT
 * @modified Caching and framework adaptation
 *
 * @framework ggLowCodeGTMKit
 */
const templateStorage = require('templateStorage');
const setCookie = require('setCookie');
const getCookieValues = require('getCookieValues');
const getUrl = require('getUrl');

const getRootDomain = function() {
    const cached = templateStorage.getItem('rd');
    if (cached) {
        return cached;
    }
    
    const testCookie = '_gtm_rd';
    let hostname = getUrl('host');
    let candidate = null;
    
    if (hostname.substring(0, 4) === 'www.') {
        hostname = hostname.substring(4);
    }
    
    const parts = hostname.split('.');
    
    for (let i = 1; i <= parts.length; i++) {
        candidate = parts.slice(-i).join('.');
        
        setCookie(testCookie, 't', {
            'domain': candidate,
            'path': '/',
            'max-age': 1,
            'secure': true
        });
        
        if (getCookieValues(testCookie).length > 0) {
            setCookie(testCookie, '', {
                'domain': candidate,
                'path': '/',
                'max-age': 0,
                'secure': true
            });
            
            templateStorage.setItem('rd', candidate);
            return candidate;
        }
    }
    
    templateStorage.setItem('rd', hostname);
    return hostname;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// getRootDomain - Direct mode
// ===============================================================================
return out(getRootDomain());
// ===============================================================================
// getRootDomain! – Apply Mode
// ===============================================================================
/*
return function() {
   return out(getRootDomain());
};
*/


___WEB_PERMISSIONS___

[
  {
    "instance": {
      "key": {
        "publicId": "get_cookies",
        "versionId": "1"
      },
      "param": [
        {
          "key": "cookieAccess",
          "value": {
            "type": 1,
            "string": "specific"
          }
        },
        {
          "key": "cookieNames",
          "value": {
            "type": 2,
            "listItem": [
              {
                "type": 1,
                "string": "gtmTestCookie"
              }
            ]
          }
        }
      ]
    },
    "clientAnnotations": {
      "isEditedByUser": true
    },
    "isRequired":