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20+ lessons available

Across 2 learning tracks

🔒 ts-playground.vercel.app

Variables

beginner

TypeScript inherits JS's three ways to declare variables…

Your task

Declare a const named greeting

index.ts__tests__.ts

1export const greeting = "Hello, World!";

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A structured lesson bank with everything you need

We have lessons covering every critical TypeScript and React concept. Every lesson comes with starter code, a solution, and test cases.

20 lessons~10 hours

Variables

Learn the difference between var, let, and const in TypeScript.

JavaScriptbeginner

Functions

Write typed functions with parameters and return types.

JavaScriptbeginner

Types & Interfaces

Define custom types and interfaces to describe the shape of your data.

JavaScriptbeginner

Interfaces & Object Types

Define the shape of objects with interfaces and type aliases.

JavaScriptbeginner

Arrays & Tuples

Type-safe collections with arrays and fixed-length tuples.

JavaScriptintermediate

Union Types & Narrowing

Model values that can be one of several types, and narrow them safely.

JavaScriptintermediate

Generics

Write reusable, type-safe functions and data structures with generics.

JavaScriptintermediate

Type Utilities

Use TypeScript's built-in utility types to transform existing types.

JavaScriptadvanced

Classes

Use TypeScript classes with constructors, methods, and access modifiers.

JavaScriptintermediate

Async / Await

Write asynchronous TypeScript with Promises, async functions, and proper typing.

JavaScriptintermediate

JSX Basics

Write your first React component with JSX syntax.

Reactbeginner

Props & Components

Build reusable components by passing data through props.

Reactbeginner

State with useState

Add interactivity to components by managing state with the useState hook.

Reactbeginner

Effects with useEffect

Run side effects in function components using the useEffect hook.

Reactintermediate

Props & Component Composition

Pass data into components with props and compose UIs from smaller pieces.

Reactbeginner

Event Handling

Handle user interactions with typed event handlers in React.

Reactbeginner

Lists & Conditional Rendering

Render dynamic lists with .map() and show content conditionally.

Reactbeginner

Custom Hooks

Extract and reuse stateful logic across components with custom hooks.

Reactintermediate

React Context

Share state across the component tree without prop drilling using useContext.

Reactintermediate

Performance

Avoid unnecessary re-renders with useMemo and useCallback.

Reactadvanced

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Interview prep

Nail your technical interview

Practice coding challenges and theoretical questions asked at Google, Meta, Amazon and more — with hints, full answers, and a live playground.

GoogleMetaAmazonMicrosoftNetflixAppleAirbnbUber

Explain the JavaScript event loop

GoogleAmazon

medium

Implement Promise.all()

MetaNetflix

medium

Explain closures in JavaScript