Interview Prep

JS100: Core Engine Mechanics

Deep dive into JavaScript's heart — from closures and the event loop to modern ES2024 features and high-performance design patterns.

Total Questions

100

Deep Topics

Core Engine

Asynchronous

Event Loop

Security

XSS/CORS

JavaScript Basics

8 questions

Functions & Scope

9 questions

Arrays & Objects

6 questions

ES6+ Modern JavaScript

5 questions

Asynchronous JavaScript

7 questions

Prototypes, Classes & OOP

4 questions

DOM & Browser APIs

5 questions

Error Handling & Debugging

2 questions

Functional Programming Concepts

4 questions

Modules & Design Patterns

4 questions

Advanced JavaScript Concepts

6 questions

Performance, Web Workers & Modern JS

40 questions

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JS100: Core Engine Mechanics

JavaScript Basics

What is JavaScript and what is it used for?

What is the difference between var, let, and const?

What are the JavaScript data types?

What is the difference between == and ===?

What is type coercion in JavaScript?

What is null vs undefined in JavaScript?

What is NaN and how do you check for it?

What is hoisting in JavaScript?

Functions & Scope

What are the different ways to declare a function?

What is scope in JavaScript?

What is a closure and why is it important?

What is the classic closure bug in loops and how do you fix it?

What is an IIFE (Immediately Invoked Function Expression)?

What is the difference between arguments object and rest parameters?

What are default parameters in functions?

What is the 'this' keyword and how does it work?

What is the difference between call(), apply(), and bind()?

Arrays & Objects

What are the most important array methods in JavaScript?

What is the difference between map() and forEach()?

What is the spread operator and how do you use it?

What is destructuring in JavaScript?

What is shallow copy vs deep copy in JavaScript?

What are the methods to iterate over objects?

ES6+ Modern JavaScript

What are template literals?

What are optional chaining (?.) and nullish coalescing (??)?

What are Map and Set in JavaScript?

What are symbols in JavaScript?

What are generators in JavaScript?

Asynchronous JavaScript

What is the Event Loop and how does JavaScript handle asynchronous code?

What is a callback and what is "callback hell"?

What is a Promise and how does it work?

What are Promise.all(), Promise.race(), Promise.allSettled(), Promise.any()?

What is async/await and how does it work?

What is the difference between microtasks and macrotasks?

What is the Fetch API and how do you handle errors properly?

Prototypes, Classes & OOP

What is the prototype chain in JavaScript?

What are ES6 Classes and how do they relate to prototypes?

What are private class fields and methods?

What is the difference between hasOwnProperty and the 'in' operator?

DOM & Browser APIs

What is the DOM?

What is event delegation and why is it useful?

What is event bubbling and capturing?

What is localStorage, sessionStorage, and cookies?

What is the Intersection Observer API?

Error Handling & Debugging

How does try/catch/finally work?

What are the different types of errors in JavaScript?

Functional Programming Concepts

What are pure functions and why are they important?

What is currying in JavaScript?

What is function composition?

What is memoization?

Modules & Design Patterns

What are ES Modules (import/export)?

What is the Module pattern?

What is the Observer pattern (publish/subscribe)?

What is the Singleton pattern?

Advanced JavaScript Concepts

What is a Proxy in JavaScript?

What is Reflect in JavaScript?

What is garbage collection in JavaScript?

What is debouncing and throttling?

What is WeakRef and FinalizationRegistry?

What is tail call optimization?

Performance, Web Workers & Modern JS

What are Web Workers?

What is the difference between setTimeout(fn, 0) and queueMicrotask()?

What is requestAnimationFrame?

What is a Service Worker?

What are JavaScript iterators and the iterable protocol?

What are async generators and async iterators?

What is Object.freeze() vs Object.seal()?