Expert Javascript Developer

Glassbox is seeking an Expert JavaScript Developer to join our global R&D team.

We are Glassbox, and our mission is to reveal the insights that empower organizations to deliver exceptional digital customer experiences.

We are growing and have been recognized by G2 as one of 2024's Top 50 Software Companies worldwide.

Our customers are the best of the best, including six of the ten largest global banks, the world's largest hotel chain, the largest healthcare provider, and the largest telecommunications company in the U.S.

Now is the perfect time to come to Glassbox and help us accelerate our global leadership position!

If you are a dynamic, successful, experienced metrics-driven leader, Glassbox might be a great fit.

Will you join us on this journey?

What you will do ?

• Develop a lightweight, efficient JavaScript script to track user interactions (clicks, scrolls, form submissions, etc.).
• Monitor AJAX requests and log network activity to capture API calls and responses.
• Detect DOM changes in real-time using MutationObservers and other native browser APIs.
• Implement efficient event listeners and minimize performance overhead.
• Hook into browser native functionalities (e.g., intercepting network requests, modifying prototypes, overriding built-in methods) to extract relevant data.
• Optimize script execution, memory usage, and CPU performance to ensure smooth operation without affecting the site.
• Work with CORS limitations, handling API authentication when required.
• Ensure cross-browser compatibility and robust error handling.
• Optimize data collection and transmission while ensuring compliance with privacy and security policies.
• Collaborate with backend teams to send collected data via APIs securely.
  
  

• 5+ years of experience in Vanilla JavaScript (ES6+).
• Strong knowledge of DOM manipulation, Event Handling, and Asynchronous JS (Promises, Fetch, WebSockets).
• Experience with MutationObserver, PerformanceObserver, and IntersectionObserver.
• Proficiency in monitoring AJAX calls, intercepting XHR/Fetch API, and modifying built-in browser functions when necessary.
• Deep expertise in performance profiling, script optimization, and debugging tools (Chrome DevTools, Lighthouse, WebPageTest, etc.).
• Deep understanding of CSS and HTML, including stylesheets, rendering behavior, and dynamic styling techniques.
• Familiarity with browser storage (LocalStorage, SessionStorage, IndexedDB) for temporary data caching.
• Understanding of security concerns (CORS, CSP, Same-Origin Policy, etc.).
• Experience in data collection while ensuring GDPR and privacy compliance.
• Ability to write clean, optimized, and well-documented JavaScript code.
  
  

• Experience with headless browsing (Puppeteer).
• Experience with Angular.
• NodeJS