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
Over two months, Jan de Mooij enhanced the mozilla/gecko-dev repository by building robust features and addressing critical bugs in the JavaScript engine. He refactored hash table internals for safer memory management and optimized interpreter performance by passing JS::Value by value, leveraging C++ and deep knowledge of compiler internals. Jan improved thread safety in string handling and introduced scalable dependency tracking for JIT compilation using IonScriptKey. He also resolved edge-case reliability issues in Promise combinators, aligning their state management with the ECMAScript specification. His work demonstrated strong skills in algorithm optimization, code refactoring, and testing, resulting in more stable, maintainable code.
Overall Statistics
Feature vs Bugs
43%Features
Repository Contributions
11Total
Bugs
4
Commits
11
Features
3
Lines of code
595
Activity Months2
Your Network
852 people
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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