Front-end engineering and CRO writing by Pascal Louwes. A/B testing, browser internals, and the unglamorous tooling that makes it all faster.https://staging.recoveryarea.nl/en-gbhttps://staging.recoveryarea.nl/ab-testing/force-variation-system/https://staging.recoveryarea.nl/ab-testing/force-variation-system/GrowthBook's native URL override bypasses every targeting rule. The QA preview tool I built keeps the rules in place — forcing only fires if the user already qualifies.Fri, 08 May 2026 00:00:00 GMTab-testinggrowthbooktoolingqahttps://staging.recoveryarea.nl/javascript/how-to-detect-user-defined-window-globals-with-javascript-enhanced/https://staging.recoveryarea.nl/javascript/how-to-detect-user-defined-window-globals-with-javascript-enhanced/An async, error-resilient globals detector: spins up an iframe baseline, categorises the diff by type, and lets you exclude known third-party noise.Fri, 19 Sep 2025 00:00:00 GMTjavascriptdebuggingab-testinghttps://staging.recoveryarea.nl/ab-testing/building-the-ultimate-a-b-testing-developer-experience/https://staging.recoveryarea.nl/ab-testing/building-the-ultimate-a-b-testing-developer-experience/How a Vite hub, a Chrome extension that hijacks production scripts, and a WebSocket reload loop turned multi-client A/B testing into hot-reloadable dev work.Fri, 12 Sep 2025 00:00:00 GMTab-testingtoolingperformancehttps://staging.recoveryarea.nl/javascript/building-a-developer-friendly-chrome-extension-script-redirector-with-live-reload/https://staging.recoveryarea.nl/javascript/building-a-developer-friendly-chrome-extension-script-redirector-with-live-reload/Inside MintMinds RequestLite: a Manifest V3 Chrome extension that redirects production script URLs to localhost and live-reloads tabs over WebSocket.Thu, 05 Jun 2025 00:00:00 GMTjavascriptchrome-extensiontoolingab-testinghttps://staging.recoveryarea.nl/javascript/how-to-list-user-defined-window-globals-with-javascript/https://staging.recoveryarea.nl/javascript/how-to-list-user-defined-window-globals-with-javascript/A tiny IIFE that compares window against a fresh iframe to list every user-defined global, grouped by type — handy for auditing third-party noise.Fri, 17 Mar 2023 00:00:00 GMTjavascriptdebuggingab-testinghttps://staging.recoveryarea.nl/javascript/how-to-simulate-clicks-on-non-supported-html-elements/https://staging.recoveryarea.nl/javascript/how-to-simulate-clicks-on-non-supported-html-elements/Why HTMLElement.click() silently fails on SVG, and the modern MouseEvent-dispatch one-liner that actually triggers the click on any element.Mon, 04 Apr 2022 00:00:00 GMTjavascriptdomab-testinghttps://staging.recoveryarea.nl/javascript/adding-dom-elements-like-a-boss/https://staging.recoveryarea.nl/javascript/adding-dom-elements-like-a-boss/A tiny config-driven helper that builds, attributes, and inserts DOM nodes in one call — the primitive that powers most of my A/B test variants.Thu, 03 Jun 2021 00:00:00 GMTjavascriptdomab-testinghttps://staging.recoveryarea.nl/javascript/my-secret-to-super-fast-ab-test-loading/https://staging.recoveryarea.nl/javascript/my-secret-to-super-fast-ab-test-loading/How wrapping querySelector in a MutationObserver kills the FOUC in A/B tests — your variant fires the instant the target element lands in the DOM.Wed, 02 Jun 2021 00:00:00 GMTjavascriptab-testingperformancebrowser-apihttps://staging.recoveryarea.nl/javascript/notify-enter-viewport-the-proper-way-intersection-observer/https://staging.recoveryarea.nl/javascript/notify-enter-viewport-the-proper-way-intersection-observer/Replacing my old rAF-based viewport tracker with IntersectionObserver — the simpler, lazier, dramatically less complicated way to fire A/B test events.Tue, 04 Feb 2020 00:00:00 GMTjavascriptbrowser-apiab-testinghttps://staging.recoveryarea.nl/ab-testing/notify-enter-viewport/https://staging.recoveryarea.nl/ab-testing/notify-enter-viewport/The original requestAnimationFrame helper that fires A/B test events when an element scrolls into view — predecessor to the Intersection Observer rewrite.Thu, 21 Jun 2018 00:00:00 GMTab-testingjquerydomhttps://staging.recoveryarea.nl/ab-testing/ab-test-jquery-performance-cheat-sheet/https://staging.recoveryarea.nl/ab-testing/ab-test-jquery-performance-cheat-sheet/Five jQuery techniques that keep A/B tests under their performance budget — selector speed, caching, chaining, event delegation, and DOM-write batching.Fri, 14 Oct 2016 00:00:00 GMTab-testingjqueryperformancecode-qualityhttps://staging.recoveryarea.nl/javascript/track-that/https://staging.recoveryarea.nl/javascript/track-that/A pocket-sized click introspection helper that JSON-stringifies the source element, its index, text, and every attribute — useful as A/B test custom tracking.Sun, 07 Feb 2016 00:00:00 GMTjavascriptanalyticsdebugginghttps://staging.recoveryarea.nl/javascript/a-smarter-console-info/https://staging.recoveryarea.nl/javascript/a-smarter-console-info/A tiny defensive wrapper that picks console.dir for objects and arrays and console.info for primitives — back when Firebug and Chrome disagreed about logging.Wed, 09 Feb 2011 00:00:00 GMTjavascriptdebugging