Summary - Memory internals

Combine heap, GC and snapshot to write a memory profiler.

Summary - Memory internals

In this group we saw Node.js memory internals: the heap/stack split, generational GC, mark-sweep, memory leaks and heap snapshots. Each addresses how memory is managed and how leaks are found.

Heap/stack: objects on the heap, primitives on the stack. Generational GC: promotes survivors between young and old generations. Mark-sweep: marks reachable from roots, sweeps the rest. Memory leak: cache growth past a limit. Heap snapshot: a list of objects with name and size. In the final lesson we combine them in a report.

The report function

The final task combines memory concepts into one report. The memoryReport() function joins region, gc and leak info with ' | '. Output: stack+heap | generational | detected.

This report summarizes three aspects of memory: regions (stack+heap), garbage collection style (generational) and leak status (detected). Inside the function you place each piece in a variable, then join them with +. regions.join('+') combines the regions. This lets you see what you learned on the console; you model the structure without the uncertainty of running real memory management.

Exercise Write the memory report

Write function memoryReport(). Define const regions = ['stack', 'heap']. Define const gc = 'generational'. Define const leak = 'detected'. Return regions.join('+') + ' | ' + gc + ' | ' + leak. Print console.log(memoryReport()).

Show example solution

function memoryReport() {
  const regions = ['stack', 'heap'];
  const gc = 'generational';
  const leak = 'detected';
  return regions.join('+') + ' | ' + gc + ' | ' + leak;
}
console.log(memoryReport());

Test yourself

Which generation is mark-sweep used for?
- Young
- Old
- Stack
- Yok
Show answer

Old — Mark-sweep is used for the old generation.
Match each concept to its role

Stack

Primitives
Heap

Objects
Generational GC

Young/old generations
Mark-sweep

Marks reachable

Next lesson: Stream backpressure

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