JavaScript Fundamentals

Types, scope, closures, the event loop, async patterns, and core language mechanics.

73 questions across 27 sections

Basic Concepts

5 questions

Primitive Types

4 questions

Reference Types

3 questions

Type Coercion

3 questions

Truthy & Falsy Values

4 questions

Equality Operators

3 questions

Object.is()

1 questions

Hoisting

5 questions

Output Questions

3 questions

Temporal Dead Zone (TDZ)

3 questions

Scope

4 questions

Lexical Environment

2 questions

Closures

5 questions

Output Questions (Closures)

1 questions

Execution Context

2 questions

Call Stack

2 questions

Functions

3 questions

Arrow Functions

2 questions

this Keyword

3 questions

call(), apply(), bind()

2 questions

Higher Order Functions

2 questions

Pure Functions

2 questions

Currying

2 questions

Partial Application

1 questions

Memoization

2 questions

Function Composition

2 questions

IIFE

2 questions

CSS

JS Objects & Async

Basic Concepts

What is JavaScript?

Why is JavaScript single-threaded?

How does JavaScript handle asynchronous tasks?

What is the JavaScript Runtime?

Difference between JavaScript Engine and Runtime.

Primitive Types

How many primitive data types exist?

Difference between Null and Undefined.

What is Symbol?

When should BigInt be used?

Reference Types

Difference between Primitive and Reference Types.

Why are objects mutable?

How are arrays stored in memory?

Type Coercion

What is Type Coercion?

Difference between Implicit and Explicit Type Conversion.

Predict the output: '5' + 1, '5' - 1, true + 1, [] + [], [] + {}, {} + []

Truthy & Falsy Values

What is Truthy?

What is Falsy?

Why is an empty array truthy?

Why is an empty object truthy?

Equality Operators

Difference between == and ===.

When should === be preferred?

Predict the output: null == undefined, null === undefined, 0 == false, '' == false

Object.is()

Difference between ==, ===, and Object.is().

Hoisting

What is Hoisting?

Why does Hoisting happen?

Does let hoist?

Does const hoist?

Does class hoist?

Output Questions

Predict: console.log(a); var a = 10;

Predict: console.log(a); let a = 10;

Predict: sayHello(); function sayHello(){ console.log("Hello"); }

Temporal Dead Zone (TDZ)

What is Temporal Dead Zone?

Why does TDZ exist?

Difference between var and let regarding TDZ.

Scope

What is Scope?

Difference between Global Scope and Block Scope.

Is var block scoped?

Is let block scoped?

Lexical Environment

What is Lexical Scope?

How does JavaScript resolve variables?

Closures

What is Closure?

Why do Closures exist?

Advantages of Closures?

Disadvantages of Closures?

Real-life examples of Closures.

Output Questions (Closures)

Predict: counter() that returns an incrementing function

Execution Context

What is Execution Context?

Difference between Creation Phase and Execution Phase.

Call Stack

What is Call Stack?

What causes Stack Overflow?

Functions

Difference between Function Declaration and Function Expression.

Difference between Normal Function and Arrow Function.

When should Arrow Functions not be used?

Arrow Functions

Difference between Arrow Function and Regular Function.

Why doesn't Arrow Function have its own this?

this Keyword

What is this?

How is this determined?

Difference between Arrow Function this and Regular Function this.

call(), apply(), bind()

Difference between call(), apply(), and bind().

When should bind() be used?