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# Magento 2 Mega Menu - Uncaught TypeError: base is not a constructor

If you’re using the [Magento 2 Mega Menu extension](https://www.weltpixel.com/mega-menu-for-magento-2.html), you may occasionally see a console error like this:

![Mega Menu console error](https://storage.crisp.chat/users/helpdesk/website/-/1/4/d/2/14d2dd8ee9ad3800/8692c292-e4df-427a-8037-36b464_1y9odce.png)

This typically results in the **menu not functioning** (e.g., dropdowns/subcategories won’t open).

---

## Cause

A **conflict with a third-party module** that also applies a **mixin** to `menu.js`. When both your theme/extension and a third-party module mix into the same component but return different structures, JavaScript may throw **“base is not a constructor.”**

---

## Solution

Edit the **mixin.js** in the conflicting third-party module so it returns both `menu` and `navigation`, not just `menu`.

**Incorrect line (current):** `return $.mage.menu;`

**Corrected return object (use this):**
    
    return {
        menu: $.mage.menu,
        navigation: $.mage.navigation
    };

---

## Important Notes

- Apply this change via the **Magento customization process** (extend/override in your custom module or theme). **Do not** edit vendor files directly, otherwise updates will overwrite your fix.
- After making the change:
  1. Redeploy static content: `php bin/magento setup:static-content:deploy -f`
  2. Flush caches from **System → Cache Management** (or `php bin/magento cache:flush`)

Once completed, the Mega Menu functionality should be restored.