What is JIT compilation in JavaScript?
Just-In-Time compilation means the engine compiles code to machine code at runtime. An interpreter runs first for fast startup, and an optimizing compiler recompiles hot code for speed.
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More FAQs in How the JavaScript Engine Works Behind the Scenes
It parses source code into an AST, JIT-compiles it to bytecode and machine code, and executes it on a single-threaded call stack while managing memory on a heap.
Node.js uses V8, the same JavaScript engine that powers Google Chrome. V8 is written in C++ and developed by Google.
When an optimized assumption breaks (like an object's shape changing), the engine discards optimized machine code and falls back to interpreted bytecode. This hurts performance.
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