E-commerce JavaScript Bug Fixing

Most single JavaScript bugs are fixed for $99 (Quick Fix, about 4 hours at $25/hr) when the error is clearly reproducible. A batch of errors, or one deep root cause like a RequireJS or Alpine conflict plus regression tests, runs $499 (Bug-Fix Sprint, ~20h @ $25/hr). Production-down emergencies use a custom on-call rate, with a $2,499 stabilization sprint (~100h @ $25/hr) for full storefront hardening. You get a fixed quote before any work starts.

It means your code read a property on something that does not exist yet, for example cart.items.length when cart is undefined. On e-commerce stores this is almost always one of three things: (1) the script ran before the DOM element it needs was rendered, (2) an async response (cart, customer data) had not arrived, or (3) a dependency failed to load. We read the stack trace to the exact line, find the null source, and fix the load order or add a proper guard, not a try/catch band-aid.

This is a RequireJS error specific to Magento. It happens when a UMD library (GSAP, Swiper, Lenis, ScrollTrigger) is loaded with a plain <script src> tag. Because Magento runs RequireJS, the library registers itself as an anonymous AMD module, never attaches to window, and your animations or sliders silently die. The fix is to load it correctly, either via a RequireJS shim/config, or by fetching it as text and injecting it with define temporarily nulled, then restored. We have hit this exact bug on real Magento and Hyvä builds.

That error means $ is not pointing at jQuery when your code runs, usually because two jQuery versions are loaded, or another library (Prototype, a marketing script) took over the $ alias. We fix it the right way: scope jQuery with jQuery.noConflict() and an explicit closure, or wire it as a proper RequireJS dependency so your script always receives the correct jQuery instance. No more guessing which $ wins.

Yes, this is common on Hyvä themes. An x-data component renders as plain HTML but never becomes interactive. The usual causes: Alpine.js loaded after the markup that uses it, a JavaScript syntax error elsewhere that halted the bundle before Alpine booted, or a typo in an Alpine directive. We restore the correct boot order, fix the broken directive, and verify the component initialises with a clean console.

It is a Content-Security-Policy block, and it breaks JavaScript just the same. Your CSP header is rejecting an inline <script> or an onclick handler because it lacks the right nonce or hash. The wrong fix is to disable CSP entirely, that removes a real security layer. We fix it correctly by adding the script to the policy with a nonce or hash, or by moving the inline code into a permitted external file, so the script runs and your CSP stays intact.

One throwing third-party tag (a chat widget, A/B tool, or affiliate pixel) can halt every script that loads after it, breaking add-to-cart or checkout. We isolate which script is throwing using the stack trace, then sandbox it so it can fail without taking your page down, loading it async/defer, wrapping it, or deferring it until after your critical JS. Your store keeps working even when the vendor’s script does not.

Yes. We fix Google Tag Manager pushing to an undefined dataLayer, custom-event listeners that throw, GA4 events firing twice, and tags loading in the wrong order. These errors quietly break your revenue attribution even when the storefront looks fine. We correct the tag and trigger order, fix the dataLayer wiring, and confirm events fire once and clean in the console and in Tag Assistant.

Staging first, always, if one exists. We reproduce the console error and validate the fix on a staging copy, then deploy to live. If you do not have a staging environment, we can spin up a quick clone or work carefully against live with a backup and a rollback plan agreed in advance. We never push an untested JavaScript change straight to your production checkout.

Yes, that is the whole point of reproduce-first. Every fix is built and verified away from production, shipped behind a backup, and the affected flow is re-tested for a clean console before we call it done. We also add a regression check so the same error cannot creep back on your next deploy. If anything regresses inside the fix warranty window, we make it right at no extra charge.

For a blocking emergency, add-to-cart or checkout dead because of a JS error, we triage in under 4 hours and usually ship a fix the same day once we have staging access. A standard, well-defined single bug is typically resolved in 24-48 hours. A batch of errors or a deep root cause is scoped as a Bug-Fix Sprint with a committed delivery date. Send the console error text and we will confirm a timeline fast.

Yes, post-upgrade JavaScript breakage is one of the most common reasons stores call us. We cover Magento (Luma and Hyvä), Shopify, WooCommerce, BigCommerce, PrestaShop, OpenCart and custom storefronts. After a platform, theme, or extension upgrade, the usual culprits are changed jQuery/RequireJS versions, removed APIs, or a third-party script that no longer matches the new markup. We diagnose what the upgrade changed and restore the broken JavaScript. See our emergency bug-fixing hub for production-down help.