JavaScript Benchmarking: A Mess of JIT Compilers, Engine Differences, and Timing Inaccuracies

Benchmarking JavaScript performance is notoriously difficult. This article highlights the challenges: the JIT compiler's dynamic optimizations lead to wildly varying results across runs; different JavaScript engines (like V8 and JavaScriptCore) exhibit significant performance disparities, with identical code performing dramatically differently; and browsers intentionally reduce timing accuracy to mitigate timing attacks, making precise measurements difficult. The author suggests using tools like d8 on the server-side for greater control over optimization levels and garbage collection, while browser-side testing relies heavily on the limited information provided by developer tools. In short, JavaScript benchmarking requires careful consideration of JIT compilation, engine variations, and timing precision, making it significantly more complex than in other languages.