Memory Basics — Complete Guide
Memory Basics — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of JavaScript Tutorial on Toolliyo Academy.
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JavaScript Tutorial · Lesson 10 of 100
Memory Basics
Basics → Objects & data → Async & DOM → Advanced → Tools → Projects
Beginner · 1 — Learn by example · ~6 min · JS Tutorial — Basics
What is this?
JavaScript stores variables in memory while your page runs. When nothing references a value anymore, the garbage collector frees that memory.
Why should you care?
Understanding memory helps you avoid leaks — timers, listeners, and global variables that never get cleaned up.
See it live — copy this example
Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.
let users = [{ name: "A" }, { name: "B" }];
users = null; // old array can be garbage-collected when unreferencedRun Example »
Edit the code below and click Run to see the result in Toolliyo’s live editor.
What happened?
- Objects stay in memory while a variable points to them.
- Setting users = null removes the reference so memory can be reclaimed.
Practice next
- Create a large array in the console and log its length.
- Set the variable to null and discuss garbage collection.
- Open DevTools Memory tab and take a heap snapshot.
- Store the array in a WeakRef and observe when get() returns undefined.
- Create two variables pointing to the same object, null one, and log the other.
Remember
Values live while referenced null removes a reference Avoid accidental globals
ScriptVerse chat history
A messaging panel caps stored messages at 500 and drops oldest entries so memory stays stable on long sessions.
Outcome: Bounded in-memory caches keep SPAs responsive on low-RAM devices.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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