JIT Compilation

Definitions

1. Just-In-Time compilation — translating bytecode or interpreted code to native machine code at runtime, right before execution. Combines the portability of interpreted languages with near-native performance by optimizing hot code paths. Used by the JVM (HotSpot), V8 (JavaScript), and .NET. The JIT can optimize based on runtime profiling data that ahead-of-time compilers can't access.

   In plain English: Compiling code to fast machine code while the program is running, based on which parts are used most.

   Example: "V8's JIT compiler profiles your JavaScript and compiles hot functions to optimized machine code — that's why Node.js is fast despite being 'interpreted.'"

Related Terms

• JIT
• Tail Call Optimization
• V8 Isolate
• Garbage Collection Pause
• AOT Compilation
• Bytecode
• ARM Architecture
• Array Buffer