JS runtime & engine

JS Engine

JS engine is a program that executes JS code. It consists of:
- Memory Heap (stores vars, objects, etc)
- Call Stack (records where in the program we are)
- Web APIs (timers, AJAX, DOM, promises)
- Event Loop (monitors msg queue and call stack)

Popular JS engines:

V8 (Chrome, Node.js)
SpiderMonkey (Firefox)
Chakra (Edge)
JavaScriptCore (Safari)

V8 JavaScript Engine

V8 is the most popular JS engine, used in Chrome and Node.js. It compiles JS code to machine code, which is faster than interpreting.

V8 has 2 compilers:

Full Compiler (optimizes code) nam
Ignition (interprets code)

Ignition Interpreter