Function declaration in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple function declaration

What is the output of this JavaScript code?

Javascript

function greet(name) {
  return `Hello, ${name}!`;
}

console.log(greet('Alice'));

A greet Alice

B Hello, Alice!

C undefined

D Error: greet is not defined

💡 Hint

Look at how the function returns a string using template literals.

The function greet returns a greeting string with the given name. Calling greet('Alice') returns 'Hello, Alice!'.

❓ Predict Output

intermediate

Function hoisting behavior

What will this code output when run?

Javascript

console.log(square(4));

function square(x) {
  return x * x;
}

A 16

B ReferenceError: square is not defined

C TypeError: square is not a function

D undefined

💡 Hint

Function declarations are hoisted in JavaScript.

Function declarations are hoisted, so square is available before its definition. square(4) returns 16.

❓ Predict Output

advanced

Function declaration inside block scope

What is the output of this code?

Javascript

if (true) {
  function sayHi() {
    return 'Hi!';
  }
}

console.log(typeof sayHi);

A ReferenceError

B "function"

C "object"

D "undefined"

💡 Hint

Function declarations inside blocks are block-scoped in modern JavaScript.

The function sayHi is block-scoped inside the if block and not available outside, so typeof sayHi is 'undefined'.

🧠 Conceptual

advanced

Difference between function declaration and function expression

Which statement correctly describes a key difference between function declarations and function expressions in JavaScript?

A Both are hoisted but only function expressions can be called before declaration.

B Function expressions are hoisted, function declarations are not.

C Function declarations are hoisted, function expressions are not.

D Neither function declarations nor function expressions are hoisted.

💡 Hint

Think about when you can call the function in the code.

Function declarations are hoisted and can be called before their definition. Function expressions are not hoisted.

❓ Predict Output

expert

Output of nested function declarations and variable shadowing

What is the output of this code?

Javascript

function outer() {
  function inner() {
    return 'inner function';
  }
  let inner = 'inner variable';
  return inner;
}

console.log(outer());

A inner variable

B inner function

C ReferenceError

D TypeError

💡 Hint

Variables declared with let shadow function declarations with the same name.

The variable inner declared with let shadows the inner function declaration, so outer returns the string 'inner variable'.