JS TrackUnderstand it, not memorise it
Master JavaScript by understanding it.
35 concepts — all with the WHY behind each behaviour. 471 exceptions, 10 practice modes, and SRS retention so you never have to re-learn the same thing twice.
⚡ 35 concepts⚠ 471 exceptions◉ 320+ practice questions🃏 SRS retention
7
Foundation
Free
3
Core
Pro
3
Advanced
Pro
471
Exceptions
With WHY
10
Modes
Practice modes
Concepts by tier
🧱
Foundation
Free· 7 concepts📦
beginnerFree
Variables & Types
Master var, let, const scoping rules and JavaScript's seven primitive types — including the exceptions that trip up every interview.
Not started
🔀
beginnerFree
Type Coercion
Understand implicit vs explicit coercion, the == vs === distinction, and the falsy values JavaScript uses when converting to boolean.
🔒 Complete prerequisites first
🔧
beginnerFree
Functions & Scope
How function declarations, expressions, and arrow functions differ in scope, hoisting, and this-binding.
🔒 Complete prerequisites first
🔒
intermediateFree
Closures
A closure is a function that remembers the variables from its birth environment. Master this and you understand 80% of JavaScript's tricky interview questions.
🔒 Complete prerequisites first
🏗
intermediateFree
Objects & Prototypes
JavaScript's object model — prototype chains, property lookup, and how ES6 class syntax maps to prototypal inheritance.
🔒 Complete prerequisites first
▤
beginnerFree
Arrays & Iteration
The array methods every JavaScript developer must know cold — map, filter, reduce — and when to reach for each one.
🔒 Complete prerequisites first
✂
beginnerFree
Destructuring
Extract values from objects and arrays concisely, set defaults, rename bindings, and use rest/spread — the patterns you see in every modern codebase.
🔒 Complete prerequisites first
⇌
Core
Pro· 3 concepts🔄
intermediatePro
The Event Loop
How JavaScript's single-threaded event loop works — call stack, task queue, microtask queue, and why microtasks always run before the next task.
🔒 Pro required to access
🤝
intermediatePro
Promises
Promises represent eventual values. Master the then/catch/finally chain, error propagation, and the combinators — all, allSettled, race, any.
🔒 Pro required to access
⏳
intermediatePro
async / await
async/await is syntactic sugar over Promises. Learn the patterns — sequential, parallel, error handling, and the subtle performance trap of await in a loop.
🔒 Pro required to access
⬡
Advanced
Pro· 3 concepts🎯
advancedPro
this & Binding
The four binding rules that determine what this refers to — and why arrow functions don't have their own this.
🔒 Pro required to access
📦
intermediatePro
Modules
ES Modules vs CommonJS — how they load, what makes them different, and when to use dynamic import for code splitting.
🔒 Pro required to access
🧩
advancedPro
Design Patterns
The GoF patterns adapted for JavaScript — singleton, factory, observer, and the module pattern — with practical examples you can use today.
🔒 Pro required to access
Ready to unlock everything?
Free
- ✓7 Foundation concepts
- ✓Variables, types, closures, prototypes
- ✓Predict-the-output challenges
- ✓True/false card drills
- ✓SRS flashcards
Pro
TechCookies Pro
- ✓All 6 Pro concepts unlocked
- ✓Async, event loop, promises, this
- ✓Modules & design patterns
- ✓Exception mastery drills
- ✓AI explanation grader