mozilla/gecko-dev
Jun 2025 – Jul 2025
2 Months active
Languages Used
C++JavaScript
Technical Skills
Algorithm OptimizationC++C++ DevelopmentCode RefactoringCompiler DesignCompiler Internals
Jan de Mooij
PROFILE
Jan De Mooij
Worked on the mozilla/gecko-dev repository over two months, focusing on enhancing the JavaScript engine’s performance, safety, and standards compliance. Delivered features such as robust hash table sizing, scalable JIT dependency tracking, and interpreter optimizations using C++ and advanced data structures. Addressed concurrency and memory management issues, including thread-safety in string handling and improved out-of-memory reporting for debugging. Refactored internal APIs and promise state management to align with ECMAScript specifications, particularly improving Promise.all and Promise.allSettled reliability. Contributed targeted tests and documentation improvements, ensuring code stability and correctness while maintaining a strong emphasis on code clarity and maintainability.
Overall Statistics
Feature vs Bugs
43%Features
Repository Contributions
11Total
Bugs
4
Commits
11
Features
3
Lines of code
595
Activity Months2
Your Network
901 peopleSame Organization
@mozilla.com401
Shared Repositories
500
Work History
July 2025
2 Commits
Jul 1, 2025July 2025: Focused on improving reliability of JavaScript Promise combinators in mozilla/gecko-dev, delivering targeted fixes and tests to ensure correct behavior under edge-case mutations, and performing internal refactoring to align promise state management with the ECMAScript spec. The changes enhance correctness, stability, and conformance for Promise.all and Promise.allSettled, with tests that prevent regressions.
2 Commits
Jul 1, 2025July 2025: Focused on improving reliability of JavaScript Promise combinators in mozilla/gecko-dev, delivering targeted fixes and tests to ensure correct behavior under edge-case mutations, and performing internal refactoring to align promise state management with the ECMAScript spec. The changes enhance correctness, stability, and conformance for Promise.all and Promise.allSettled, with tests that prevent regressions.
July 2025
June 2025
9 Commits • 3 Features
Jun 1, 2025June 2025 performance review for mozilla/gecko-dev: Focused on safety, performance, and scalable JIT infrastructure. Delivered concrete features and fixed critical issues with clear business impact: stability in the JS engine, improved interpreter efficiency, and robust memory/error reporting for debugging and profiling.
June 2025
9 Commits • 3 Features
Jun 1, 2025June 2025 performance review for mozilla/gecko-dev: Focused on safety, performance, and scalable JIT infrastructure. Delivered concrete features and fixed critical issues with clear business impact: stability in the JS engine, improved interpreter efficiency, and robust memory/error reporting for debugging and profiling.
Activity
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Quality Metrics
Correctness90.0%
Maintainability90.0%
Architecture86.4%
Performance84.6%
AI Usage20.0%
Skills & Technologies
Programming Languages
C++JavaScript
Technical Skills
Algorithm OptimizationC++C++ DevelopmentCode RefactoringCompiler DesignCompiler InternalsConcurrencyData StructuresDebuggingDocumentation ImprovementInternal API RefactoringJIT CompilationJavaScriptJavaScript DevelopmentJavaScript Engine
Repositories Contributed To
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