JavaScript & TypeScript Interview Prep
Coercion, closures, the event loop and the type system — drilled the way interviews actually ask them.
200 original practice questions across 6 domains, weighted the way interviews actually ask them. Like everything on this site, it runs entirely in your browser: no account, no tracking of your answers, no data leaving your device. Questions are written from the official documentation and versioned to current behavior.
The 6 domains
Types, Coercion & Equality
15%Primitives, truthiness, == versus ===, ToPrimitive, NaN and -0, floating point, and the conversion puzzles interviewers open with.
study →Scope, Closures & Functions
17%var versus let, hoisting and the temporal dead zone, closures over loop variables, currying, call/apply/bind, and closure-driven memory leaks.
study →Objects, Prototypes & Classes
15%this binding, the prototype chain, class syntax and private fields, getters, descriptors, super, and shallow-copy traps.
study →Async, Promises & the Event Loop
20%Microtasks versus tasks, promise combinators, async/await, cancellation with AbortController, and the output-order puzzles that decide screens.
study →TypeScript Type System
20%Structural typing, unknown versus any, narrowing and type predicates, generics, utility and mapped types, satisfies, and conditional types with infer.
study →Modules, Iteration & Generators
13%ESM versus CommonJS, live bindings, circular imports, tree shaking, the iterator protocol, generators, and async iteration.
study →How to use this track
- Curriculum — read the study notes for each domain, weighted like real interview loops.
- Practice — drill individual domains with instant explanations, then take the 50-question timed mock exam.
- Cheat sheet — the memorizable facts, condensed for the night before.
Other tracks: React
Independent community study resource — not affiliated with or endorsed by Oracle, Microsoft or Ecma International. JavaScript is a trademark of Oracle Corporation; TypeScript is a trademark of Microsoft Corporation. All questions and study notes are original, written from MDN, the ECMAScript specification and the TypeScript handbook. Everything runs in your browser; nothing you answer is stored or transmitted.