Learn Concepts

Visual, interactive explanations of core concepts.
Understand the "why" before practicing the "how".

162 interactive topics across 19 categories

112 topics

JavaScript Concepts

Core JS mechanics: Closures, Event Loop, Prototypes, This keyword, and runtime internals.

Fundamentals (58)Beginner Basics (18)Core Mechanics (13)Advanced (6)Browser (6)
20 topics

DSA Concepts

Data Structures & Algorithms fundamentals: Arrays, Hash Tables, Stacks, Queues, Big O, and more.

Foundations (2)Data Structures (8)Algorithms (4)Patterns (0)
30 topics

React Concepts

React fundamentals: Hooks, Virtual DOM, Component Patterns, Performance, and Server Components.

Foundations (5)Basic Hooks (4)Advanced Hooks (5)Rendering (5)Patterns (6)Performance (5)

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Top interview concepts

6m

Scope Basics: Global, Function & Block

Where variables live and are accessible

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12m

Array Iteration: forEach, map, filter, find

Declarative array processing methods

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10m

The Infamous Loop Closure Bug

Why var + closures in loops cause bugs

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JS Interview CheatsheetAll key points in one page
DSA Learning RoadmapStep-by-step learning path