JavaScript Scope & Hoisting - Practice Questions 2026 - Free Online Course

Mastering JavaScript requires more than just reading syntax; it requires a deep understanding of how the engine handles data and execution. These JavaScript Scope & Hoisting Practice Questions are designed to bridge the gap between theoretical knowledge and technical interview readiness. By focusing on the "under the hood" mechanics of JavaScript, this course ensures you won't be caught off guard by tricky code snippets or complex closures.

Why Serious Learners Choose These Practice Exams

Serious learners choose this course because it moves beyond surface-level definitions. While many tutorials explain what a variable is, few challenge you to predict the behavior of that variable within nested scopes or during the creation phase of an execution context. These exams provide:

Deep Technical Insight: Understand the "why" behind every result.
Confidence for Interviews: Many of these questions are modeled after real-world technical screening tests used by top tech firms.
Logical Rigor: You will learn to think like the JavaScript engine, identifying potential bugs before they even hit the console.

Course Structure

The curriculum is meticulously organized to take you from foundational logic to professional-grade problem-solving.

Basics / Foundations
This section focuses on the fundamental declaration types: var, let, and const. You will learn the primary differences in how these keywords interact with the global object and their initial values.
Core Concepts
Here, we dive into Global and Function scope. You will practice identifying where variables are accessible and how the JavaScript engine searches for identifiers within a single level of scope.
Intermediate Concepts
This module introduces Block scope and the Temporal Dead Zone (TDZ). You will learn how modern JavaScript prevents common errors by restricting variable access before declaration.
Advanced Concepts
Focus on nested scopes, Lexical Environment, and Closures. This section challenges your ability to track variable values across multiple function calls and execution contexts.
Real-world Scenarios
Test your knowledge against "dirty" code. These questions simulate real-world debugging scenarios where scope leaks or hoisting issues lead to unexpected production bugs.
Mixed Revision / Final Test
A comprehensive exam that blends all previous topics. This mimics a high-pressure interview environment where you must switch between different conceptual frameworks rapidly.

Sample Practice Questions

QUESTION 1

What will be the output of the following code?

JavaScript

console.log(a);

var a = 10;

OPTION 1: 10
OPTION 2: ReferenceError: a is not defined
OPTION 3: undefined
OPTION 4: null
OPTION 5: TypeError
CORRECT ANSWER: OPTION 3
CORRECT ANSWER EXPLANATION: Due to Hoisting, the declaration var a is moved to the top of its scope during the creation phase. However, the assignment happens during the execution phase. Therefore, at the time of the console log, the variable exists but hasn't been assigned a value yet, resulting in undefined.
WRONG ANSWERS EXPLANATION: * Option 1: Wrong because the assignment 10 happens after the log.
- Option 2: Wrong because var is hoisted; a ReferenceError only occurs if the variable was never declared.
- Option 4: Wrong because JavaScript defaults uninitialized variables to undefined, not null.
- Option 5: A TypeError occurs when you perform an operation on a value of the wrong type; here, we are simply accessing a variable.

QUESTION 2

What occurs in this block?

JavaScript

{

console.log(b);

let b = 20;

}

OPTION 1: 20
OPTION 2: undefined
OPTION 3: null
OPTION 4: ReferenceError
OPTION 5: 0
CORRECT ANSWER: OPTION 4
CORRECT ANSWER EXPLANATION: Variables declared with let and const are hoisted but remain uninitialized in the Temporal Dead Zone (TDZ) until the code reaches the declaration. Accessing them before that point triggers a ReferenceError.
WRONG ANSWERS EXPLANATION:
- Option 1: Wrong because let does not allow access before the line of declaration.
- Option 2: Wrong because let does not initialize to undefined during hoisting like var does.
- Option 3: Wrong because null is an intentional assignment, never a default engine state.
- Option 5: Wrong as there is no logic here that would result in a numeric zero.

QUESTION 3

Which scope does a variable declared with var inside an if block belong to?

OPTION 1: Block Scope
OPTION 2: Local Scope only
OPTION 3: The nearest Function or Global Scope
OPTION 4: It becomes a constant
OPTION 5: It is deleted after the block ends
CORRECT ANSWER: OPTION 3
CORRECT ANSWER EXPLANATION: var is function-scoped, not block-scoped. If it is placed inside an if block or for loop, it "leaks" out and belongs to the surrounding function or the global execution context.
WRONG ANSWERS EXPLANATION:
- Option 1: Wrong because only let and const respect block boundaries.
- Option 2: Local scope is too vague; var specifically looks for the function boundary.
- Option 4: Wrong as var is explicitly for variables that can be reassigned.
- Option 5: Wrong because var declarations persist in the memory of the containing function.