hasLocalStorageKey — GTM Variable Template for GTM

VARIABLES › GTM

hasLocalStorageKey EXTENDED GTM

Direct (.tpl) Apply (.tpl) Add to GTM

Check whether a specific key exists in localStorage.

---

When to Use This

---

GTM Configuration

This is what you'll see when you open this variable in Google Tag Manager. Hover the icons for details.

Read-only Preview

hasLocalStorageKey

Storage Key

💾 The key to check in localStorage.

Supported formats:
  ✓ String

Input Setup

Input Function (optional)

⚙️ Optional pre-processing function applied to the key before internal logic (e.g., normalize case, add prefix). Internal transformations will still apply afterward.

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the result before returning it (e.g., val => val ? 'Exists' : 'Missing', val => !val for negation). Useful for chaining transformations on the output.

---

Related Variables

Same category: GTM

→ document.title → estimateReadingTime → findClosestElement → gaEcommerceEventList → gaLeadGenerationEventList → getCookieValue → getDataLayerByEvent → getDataLayerCurrent → getDataLayerValue → getElementAttribute → getGaMeasurementIds → getLocalStorage → getPersistedDataLayerValue → getRootDomain! → gtmIsDebugMode → gtmIsPreviewMode → isGrantedAdPersonalization → isGrantedAdStorage → isGrantedAdUserData → isGrantedAnalyticsStorage → isGrantedFunctionalityStorage → isGrantedPersonalizationStorage → isGrantedSecurityStorage → ⚡ COMMAND TABLE › Lazy (Advanced)

---

Under the Hood

📜 View Implementation Code

/**
 * Checks whether a given key exists in localStorage.
 *
 * @param {string} data.key - The key to check in localStorage.
 * @param {Function|string} [data.out] - Optional output handler: function to transform result or string with format.
 *
 * Direct-mode specific parameters:
 * @param {Function} [data.pre] - Optional pre-processor function to transform key before checking.
 *
 * @returns {boolean} True if the key exists in localStorage, false otherwise.
 *
 * @framework ggLowCodeGTMKit
 */

const localStorage = require('localStorage');

const hasLocalStorageKey = function(key) {
    return localStorage.get(key) !== null;
};

const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);

// ===============================================================================
// hasLocalStorageKey - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const processedKey = applyCast(data.pre, data.key);
return out(hasLocalStorageKey(processedKey));
// ===============================================================================
// hasLocalStorageKey() – Apply Mode
// ===============================================================================
/*
return function(value) {
   return out(hasLocalStorageKey(value));
};
*/


___WEB_PERMISSIONS___

[
  {
    "instance": {
      "key": {
        "publicId": "access_local_storage",
        "versionId": "1"
      },
      "param": []
    },
    "isRequired": true
  }
]