[100% Off] Javascript Advanced Functions - Practice Questions 2026

JavaScript Advanced Functions 120 unique high-quality test questions with detailed explanations!

Added on February 21, 2026 IT & Software 4 min read

What you’ll learn

Master closures
callbacks
and IIFEs with clear understanding of scope and execution behavior.
Write efficient
reusable functions using higher-order functions and functional patterns.
Debug and fix common issues like callback hell
scope bugs
and closure-related memory problems.
Apply advanced function concepts to real-world interview problems and coding scenarios.

Requirements

Basic understanding of JavaScript syntax (variables
functions
loops
and arrays).
Familiarity with HTML and browser console for practicing JavaScript examples.
A computer or laptop with internet access and any modern web browser.
Willingness to practice coding and solve interview-style questions regularly.

Description

Mastering JavaScript advanced functions is the definitive turning point between being a coder and being an engineer. This comprehensive practice exam course is specifically designed to bridge that gap, providing you with a rigorous environment to test your knowledge of closures, recursion, functional programming, and more.

Why Serious Learners Choose These Practice Exams

Serious learners understand that watching tutorials is only half the battle. True mastery comes from being able to debug complex logic and predict execution behavior under pressure. This course provides:

Deep Concept Validation: We don’t just ask what a function does; we ask how it behaves within specific execution contexts.
Detailed Feedback Loops: Every single question is accompanied by an exhaustive explanation, ensuring you learn from every mistake.
Industry Standards: The questions are modeled after real-world technical interviews at top-tier tech companies.

Course Structure

Our curriculum is organized into six distinct levels to ensure a logical progression of difficulty:

Basics / Foundations: We start by reinforcing your understanding of function declarations versus expressions, arrow function syntax, and the fundamental behavior of the “return” keyword.
Core Concepts: This section dives into the mechanics of Scope and Hoisting. You will be tested on how JavaScript handles variable accessibility and function availability during the creation phase.
Intermediate Concepts: Here, we explore Closures and Higher-Order Functions. You will learn to identify how functions retain access to their lexical environment even after the outer function has closed.
Advanced Concepts: This level covers complex topics like Currying, Function Composition, Recursion, and the explicit binding of “this” using Call, Apply, and Bind.
Real-world Scenarios: You will encounter questions based on common development tasks, such as debouncing, throttling, and managing asynchronous function flows.
Mixed Revision / Final Test: A comprehensive evaluation that pulls questions from every category to simulate a high-stakes certification or interview environment.

Sample Practice Questions

QUESTION 1

What will be the output of the following code?

JavaScript

function outer() {

let count = 0;

return function() {

count++;

return count;

};

}

const instance = outer();

instance();

console. log(instance());

OPTION 1: 0
OPTION 2: 1
OPTION 3: 2
OPTION 4: undefined
OPTION 5: ReferenceError
CORRECT ANSWER: OPTION 3
CORRECT ANSWER EXPLANATION: This is a classic example of a Closure. When outer() is called, it returns the inner function. The variable count is preserved in the inner function’s lexical environment. The first call instance() increments count to 1. The second call, which is inside the console. log(), increments it to 2 and returns that value.
WRONG ANSWERS EXPLANATION:
- OPTION 1: Incorrect because the increment operator count++ has already run once before the logged call.
- OPTION 2: Incorrect because this would be the result of the first call only.
- OPTION 4: Incorrect because the function explicitly returns the variable count.
- OPTION 5: Incorrect because count is properly defined within the scope of the outer function.

QUESTION 2

Which method should you use to call a function immediately while passing an array as individual arguments?

OPTION 1: Function. prototype. bind()
OPTION 2: Function. prototype. apply()
OPTION 3: Function. prototype. call()
OPTION 4: Function. prototype. map()
OPTION 5: Function. prototype. slice()
CORRECT ANSWER: OPTION 2
CORRECT ANSWER EXPLANATION: The apply() method calls a function with a given this value, and arguments provided as an array (or an array-like object). This allows the elements of the array to be treated as individual arguments to the function.
WRONG ANSWERS EXPLANATION:
- OPTION 1: bind() creates a new function but does not execute it immediately.
- OPTION 3: call() accepts an argument list, not an array. To use an array with call(), you would need to use the spread operator.
- OPTION 4: map() is an Array prototype method used for transformation, not for changing function execution context.
- OPTION 5: slice() is used to extract a portion of an array and has no relation to function invocation.

Welcome to the Best Practice Exams

Welcome to the best practice exams to help you prepare for your JavaScript Advanced Functions. This course is designed to give you the confidence you need to succeed in any technical environment.