If you’re a developer or a business owner managing a team, you might have come across this frustrating error in your web applications:

or

It often shows up when navigating between pages, loading content dynamically with AJAX, or using Single Page Application frameworks like Inertia.js, Turbolinks, or Vue Router. While it looks like a trivial JavaScript bug, for many businesses it leads to broken forms, failed user submissions, and eventually poor user experience and lost conversions.

At CodeHunger, we frequently solve these issues while building and maintaining scalable applications for startups, ecommerce brands, and enterprise clients. Let’s break down why these errors occur, how to fix them, and how we ensure such bugs never reach production for our clients.

💡 Why Does “select2 is not a function” Happen?

Here’s the real cause in simple terms:

✅ Select2 is a jQuery plugin that enhances your <select> dropdowns with search, theming, and multiple select support.

✅ The error means jQuery cannot find the Select2 function, because:

1. The Select2 library isn’t loaded before you call it.
2. Multiple jQuery versions are loaded, and the plugin is attached to a different instance.
3. You are loading HTML dynamically (AJAX or SPA) but not re-initializing Select2 on new elements.

The same logic applies to jQuery Mask Plugin or any other jQuery plugin that modifies input fields.

🔍 Real Client Example

Recently, while maintaining an ecommerce admin panel for a retail client, their team reported:

“Filters stop working when navigating between categories. The dropdown enhancements disappear randomly.”

On debugging, we found:

1. They used Inertia.js for navigation (Laravel + Vue stack).
2. Select2 was initialized in a standard $(document).ready() block.
3. Since Inertia replaces page content without full reloads, document.ready never re-fired, leaving new dropdowns uninitialized.

We fixed it by initializing Select2 inside Inertia’s mounted lifecycle hook and tested navigation extensively before deploying to production.

🛠️ General Solutions for These Errors

Here’s our proven approach:

✅ 1. Check Script Loading Order

Always load jQuery first, then plugins, then your initialization code:

Why it matters: If app.js runs before Select2 is loaded, $().select2() is undefined.

✅ 2. Avoid Multiple jQuery Versions

If two different jQuery versions are included (often via CDN + local build), plugins attach to the first instance while your code uses the second. Remove duplicates after inspecting the browser console’s network tab.

✅ 3. Re-Initialize Plugins After Dynamic Loads

When using AJAX:

For frameworks like Inertia.js, Turbolinks, or Vue Router, initialize inside their page load or mounted events:

✅ 4. Always Test Navigation and Dynamic Content

We include this as a mandatory checklist item before deploying frontend features. Missing it leads to errors surfacing in production, which is what businesses want to avoid.

🎯 Why Fixing Such Errors Matters for Your Business

Many founders or managers see these as “small UI bugs,” but here’s what they truly impact:

❌ Broken forms lead to abandoned checkouts or lost leads

❌ Admin panel errors increase operational inefficiency

❌ Frontend bugs reduce user trust in your brand

❌ Time spent debugging these later increases development costs

🏆 How We Solve It for Clients

At CodeHunger, our approach goes beyond just fixing the bug:

✅ Root Cause Analysis – We identify why it happened in your current stack.

✅ Long Term Fixes – Implement framework-compatible initializations.

✅ Refactoring Recommendations – Suggest better plugin alternatives if your tech stack is evolving.

✅ Regression Testing – Ensure no similar JS initialization issues exist across modules.

✅ Code Review Guidelines – We document such learnings to prevent future recurrences within your team.

🚀 Need Help Fixing Similar Frontend Bugs?

We specialize in building bug-free, scalable web applications using Laravel, Vue.js, React, jQuery, and modern stacks. Whether it’s an existing app with JS bugs or a new product you’re building, our team ensures:

✔️ Smooth UI interactions

✔️ Clean and maintainable frontend code

✔️ Faster development with reduced future bug fixes

💬 Let’s Build Together

👉 Facing UI bugs like these?

👉 Need your admin panel or ecommerce frontend optimized?

💡 Book a free technical consultation with our team today. Let’s ensure your users get the seamless experience they deserve.

📞 Contact Us Now

✨ Final Thoughts

“select2 is not a function” or “mask is not a function” errors might seem small, but for businesses aiming for premium user experience, they are worth fixing right and fixing fast. Never let a simple script loading issue cost you revenue or user trust.