How JS Runs
Scope Chain
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Closures
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Prototype
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Class & Inheritance
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Event Loop
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EN
Scope Chain Visualizer
Select preset example or edit/paste custom code
Multi-Level Scope Lookup
Variable Shadowing
Lexical Scope vs Call Stack
ES6 Block Scope Isolation
Step 0 of 0
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Step
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Run
Press → (Step) or Space (Run)
◀
▶ Run Auto
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Phase 1: Compilation
(Hoisting & Memory Setup)
➔
Phase 2: Execution
(Line-by-line Evaluation)
Execution Step Breakdown
Press "→" / click "▶" to step line-by-line, or press "Space" / click "▶ Run" for auto-play.
Scope Chain
Lexical Environment Chain: Inner Scope → Outer [[Scope]] → Global (GO)
No active scope chain
CALL STACK
— Stack of Execution Contexts (LIFO)
LIFO Stack Frames
Global Execution Context (GEC)
▶ Active Frame
HEAP & MEMORY SPACE
— Allocated Objects (GO, AO, FunctionObjects, ER)
ECMAScript Heap Area
No objects in memory
Console Output
console.log(...) Stream
No output generated yet
