On this page · sections

JavaScript Interview Prep

Master JavaScript. Think like a senior. Code with confidence.

A focused prep sheet for Senior Frontend interviews — core JavaScript, runtime behavior, async programming, and coding problems.

Senior Frontend · Core JS · Coding Round

🚀 Core JavaScript

#	Level	Topic	Scope
01	Easy	Variables, Scope & Hoisting	`var` vs `let` vs `const` · hoisting · TDZ · block/function scope · per-request state
02	Easy	Types, Coercion & Equality	primitives vs references · `typeof` · `==` vs `===` · `Object.is` · coercion · truthy/falsy
03	Medium	Execution Context & Closures	execution context · call stack · lexical environment · closures · private state · stale closures
04	Medium	Functions & `this`	declarations vs expressions · arrow functions · `this` · `call` · `apply` · `bind` · `new`
05	Medium	Prototypes, Classes & Inheritance	`new` · prototype chain · classes · `extends` · `super` · `instanceof` · composition
06	Medium	Objects, Arrays & Descriptors	spread · destructuring · mutation · property descriptors · getters/setters · property keys
07	Hard	Event Loop & Runtime	call stack · tasks · microtasks · `queueMicrotask` · timers · rendering · runtime vs host
08	Medium	Promises, Async & Concurrency	Promise states · chaining · error propagation · `async/await` · sequential vs parallel
09	Medium	DOM Events, Scripts & Modules	capture · target · bubble · delegation · `async` · `defer` · ESM · CommonJS
10	Medium	Collections, Iterables & Generators	`Map` · `Set` · `WeakMap` · `WeakSet` · iterables · iterators · generators · `yield`
11	Medium	Error Handling & Cancellation	`try/catch` · custom errors · Promise errors · `AbortController` · timeout · cancellation
12	Hard	Memory & Garbage Collection	reachability · GC · memory leaks · closures · event listeners · `WeakMap` · `WeakRef`
13	Hard	Rendering, Performance & Workers	reflow · repaint · long tasks · main thread · Web Workers · `postMessage` · performance
14	Hard	Proxy, Caching & Invalidation	Proxy traps · cache keys · memoization · LRU · TTL · invalidation strategies
15	Mixed	Patterns, FP & Architecture	Observer · Strategy · modules · composition · purity · immutability · functional patterns

💻 JavaScript Coding

#	Level	Topic	Scope
16	Medium	Core JS Polyfills	`call` · `apply` · `bind` · `map` · `filter` · `reduce`
17	Easy	Array & Object Utilities	`flatten` · `groupBy` · `unique` · `chunk` · `flattenObject`
18	Medium	Deep Clone & Equality	deep clone · deep equality · circular references · `Map` · `Set` · `RegExp` · deep merge
19	Medium	Pipe, Compose & Curry	`pipe` · `compose` · curry · partial application · placeholders · uncurry
20	Medium	Debounce & Throttle	leading/trailing execution · delay · cancellation · `cancel`
21	Medium	Promise Polyfill	Promise states · `then` · chaining · `catch` · `finally` · `all` · `race`
22	Hard	Task Scheduler	concurrency limit · queue · task execution · rejection · completion · `finally`
23	Hard	EventEmitter	`on` · `off` · `once` · `emit` · listener management · PubSub
24	Hard	LRU Cache	`get` · `put` · `Map` · doubly linked list · eviction · O(1) operations

⚡ Quick Revision

#	Level	Topic	Scope
25	Mixed	Top 30 Tricky JS Output Questions	hoisting · closures · `this` · coercion · promises · event loop
26	Mixed	Top 20 HTML & CSS Interview Q&A	semantic HTML · CSS specificity · box model · flexbox · grid · accessibility

Recommended path: Core JS → Polyfills → Utilities → Async → Scheduler → EventEmitter → LRU → Quick Revision

Understand it → Implement it → Explain it → Handle the follow-up.