Memory Leaks — Complete Guide
Memory Leaks — 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 74 of 100
Memory Leaks
Basics ✓ → Objects & data ✓ → Async & DOM ✓ → Advanced ✓ → Tools → Projects
Advanced · 5 — Testing & tools · ~10 min · JS Performance & Security
What is this?
Memory leaks happen when your code keeps references to data that should be freed — detached DOM nodes, forgotten timers, global caches.
Why should you care?
Long-lived SPAs slow down and crash tabs if leaks accumulate.
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.
// Leak pattern: listener never removed
// const btn = document.getElementById("x");
// btn.addEventListener("click", onClick);
// document.body.removeChild(btn); // listener may keep btn aliveRun Example »
Edit the code below and click Run to see the result in Toolliyo’s live editor.
What happened?
- Remove listeners with removeEventListener when removing DOM.
- Clear intervals.
- WeakMap helps for metadata.
Practice next
- Study listener-on-removed-node leak pattern.
- Take heap snapshot in Memory tab.
- Remove listeners with removeEventListener.
- Fix leak by calling removeEventListener before removeChild.
- Use AbortController to cancel fetch on SPA navigation.
Remember
Remove listeners and timers Avoid detached DOM references Profile heap over time
ScriptVerse long-lived SPA
After 8 hours on trading dashboard, uncleared WebSocket listeners caused tab RAM to triple.
Outcome: Leak fixes keep enterprise ScriptVerse sessions stable for all-day users.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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