Call stack
The call stack shows the currently active execution contexts.
- The global frame is the outer script-level context.
- Function frames appear when a function is called.
- A frame disappears when that function returns.
JavaScript memory model
Node.js Variable Memory Simulator
Step through small JavaScript examples and watch primitive values, object references, stack frames, and heap objects change.
Primitive value
Reference
Heap object
Code
Call stack
bindings live hereHeap
objects live hereConceptual memory table
not physical addresses| Area | Name | Kind | Holds |
|---|
Learning materials
What this simulator teaches
Use these notes as a companion to the scenarios. The visuals are conceptual: they explain observable JavaScript behavior, not exact V8 memory addresses.
In this scenario
Visual model basics
Frame types
A frame is a conceptual container for local bindings.
- Global bindings are visible from top-level code.
- Function bindings include parameters and local variables.
- Shadowed names can exist in multiple frames at once.
Heap
The heap represents objects, arrays, functions, and retained closure environments.
- Object and array properties are shown inside heap cards.
- Multiple bindings can reference the same heap object.
- Heap entries remain shown while some binding or closure still reaches them.