JavaScript — Free Quiz Course

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Test and sharpen your JavaScript knowledge: values and types, closures, objects, the event loop, promises, this, prototypes, and modules.

5 chapters, 50 questions. Free, no signup. Progress is saved in your browser.

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  1. Chapter 1: Values & Types
    Primitives vs objects, typeof quirks, type coercion, equality, NaN, and the difference between null and undefined.
  2. Chapter 2: Functions, Scope & Closures
    How scope works in JavaScript: var vs let, hoisting, closures, arrow functions, default parameters, and IIFEs.
  3. Chapter 3: Objects & Arrays
    References vs copies, destructuring, spread, array methods like map and filter, sorting gotchas, and object keys.
  4. Chapter 4: Async JavaScript
    The event loop, callbacks, promises, async/await, microtasks vs macrotasks, and common async mistakes.
  5. Chapter 5: this, Prototypes & Classes
    How this is determined, prototype chains, classes and inheritance, ES modules, and what new actually does.

Course completed

You finished every chapter — best score/.

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How it works

Each chapter is a short quiz: one question at a time, with immediate feedback and an explanation after every answer. Wrong answers teach you as much as right ones.

Your progress is stored in your browser (localStorage), so you can leave and come back any time. Nothing leaves your machine, and there is no account or signup.

The questions are based on tutorials published on this site — every chapter links the related posts, and you can grab the free JavaScript Handbook to study the whole topic.