Learn Concepts

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

202 interactive topics across 28 categories

122 topics

JavaScript Concepts

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

Fundamentals (58)Beginner Basics (18)Advanced (16)Core Mechanics (13)Browser (6)
22 topics

DSA Concepts

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

Foundations (2)Data Structures (8)Algorithms (5)Patterns (1)
33 topics

React Concepts

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

Foundations (5)Basic Hooks (4)Advanced Hooks (6)Rendering (5)Patterns (7)Performance (6)
15 topics

TypeScript Concepts

Type system mastery: Generics, Utility Types, Conditional Types, React + TS patterns, and interview prep.

Foundations (3)Utility Types (3)Advanced (3)React + TS (3)Interview (3)
10 topics

System Design

Frontend system design: RADIO framework, component architecture, data fetching, and case studies.

Framework (2)Core Patterns (3)Performance (3)Case Studies (2)

Jump straight in

Top interview concepts

6m

Scope Basics: Global, Function & Block

Where variables live and are accessible

Start learning
12m

Array Iteration: forEach, map, filter, find

Declarative array processing methods

Start learning
10m

The Infamous Loop Closure Bug

Why var + closures in loops cause bugs

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