JavaScript

Closures and scope

this, prototypes overview

Modules (ESM) basics

Error handling patterns

Data structures in JS (Map/Set)

Promises patterns

async/await and error boundaries

Fetch + abort controller overview

Event loop overview

Concurrency patterns overview

Events and delegation

Forms handling patterns

Rendering performance basics

Web APIs overview

Security: XSS basics

npm scripts

Bundlers overview (Vite/Webpack)

Lint/format basics

Env and build modes overview

Debugging with DevTools

Unit tests (Vitest/Jest) basics

Mocking and spies basics

Testing async code

E2E overview (Playwright/Cypress)

CI basics for JS tests