Why functions are needed in Javascript - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function named greet.

Javascript

function [1]() {
  console.log('Hello!');
}

Drag options to blanks, or click blank then click option'

AsayHello

Bgreet

Chello

Dwelcome

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than asked.

The function name should be greet as asked.

2fill in blank

medium

Complete the code to call the function greet.

Javascript

[1]();

Drag options to blanks, or click blank then click option'

Agreet

Bwelcome

Chello

DsayHello

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a function name that was not defined.

To call the function named greet, write greet().

3fill in blank

hard

Fix the error in the function call to greet.

Javascript

greet[1];

Drag options to blanks, or click blank then click option'

A()

B{}

C[]

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Using braces or brackets instead of parentheses.

Functions are called with parentheses (). Missing them causes an error.

4fill in blank

hard

Fill both blanks to create a function that adds two numbers and returns the result.

Javascript

function add(a, b) {
  return a [1] b[2];
}

Drag options to blanks, or click blank then click option'

A*

B-

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Adding extra characters after the second variable.

The operator to add two numbers is +. No extra character is needed after b.

5fill in blank

hard

Fill all three blanks to create a function that takes a name and prints a greeting.

Javascript

function [1]([2]) {
  console.log('Hello, ' + [3] + '!');
}

Drag options to blanks, or click blank then click option'

Agreet

Bname

DsayHello

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the parameter and inside the message.

Using a different function name than asked.

The function name is greet, the parameter is name, and the same parameter is used inside the message.

Practice

1. Why do we use functions in JavaScript?
function greet() { console.log('Hello!'); }

easy

A. To store data permanently

B. To make the program run faster

C. To reuse code and avoid repeating the same instructions

D. To create new variables automatically

Solution

1. Step 1: Understand the purpose of functions

   Functions group code so it can be used multiple times without rewriting.

2. Step 2: Identify the benefit in the example

   The greet function can be called many times to print 'Hello!' without repeating code.

3. Final Answer:

   To reuse code and avoid repeating the same instructions -> Option C

4. Quick Check:

   Functions help reuse code = C [OK]

Hint: Functions help reuse code easily [OK]

Common Mistakes:

• Thinking functions make code run faster
• Confusing functions with variables
• Believing functions store data permanently

2. Which of the following is the correct way to define a function named sayHi in JavaScript?

easy

A. function: sayHi() { console.log('Hi'); }

B. def sayHi() { console.log('Hi'); }

C. func sayHi() { console.log('Hi'); }

D. function sayHi() { console.log('Hi'); }

Solution

1. Step 1: Recall JavaScript function syntax

   JavaScript uses the keyword function followed by the name and parentheses.

2. Step 2: Check each option's syntax

   Only function sayHi() { console.log('Hi'); } uses correct JavaScript syntax for defining a function.

3. Final Answer:

   function sayHi() { console.log('Hi'); } -> Option D

4. Quick Check:

   JavaScript functions start with 'function' keyword = D [OK]

Hint: JavaScript functions start with 'function' keyword [OK]

Common Mistakes:

• Using Python or other language keywords like def or func
• Adding colon after function keyword
• Missing parentheses after function name

3. What will be the output of this code?

function add(a, b) {
  return a + b;
}
console.log(add(3, 4));

medium

A. 7

B. 34

C. undefined

D. Error

Solution

1. Step 1: Understand the function behavior

   The function add takes two numbers and returns their sum.

2. Step 2: Calculate the result of add(3, 4)

   3 + 4 equals 7, so the function returns 7.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add numbers inside function to get sum [OK]

Common Mistakes:

• Concatenating numbers as strings (getting 34)
• Forgetting to return a value (getting undefined)
• Syntax errors causing runtime error

4. Find the error in this function and choose the fix:

function greet() {
  console.log('Hello!')
}
greet;

medium

A. Add a return statement inside greet

B. Change greet; to greet();

C. Remove the semicolon after console.log

D. Rename function to greetUser

Solution

1. Step 1: Identify how the function is called

   The function is defined correctly but called as greet; which does not execute it.

2. Step 2: Correct the function call syntax

   To run the function, parentheses are needed: greet();

3. Final Answer:

   Change greet; to greet(); -> Option B

4. Quick Check:

   Functions run with parentheses = B [OK]

Hint: Call functions with parentheses () [OK]

Common Mistakes:

• Calling function without parentheses
• Thinking return is needed to print
• Changing function name unnecessarily

5. You want to write a program that prints a greeting message multiple times without repeating code. Which approach is best?

hard

A. Use a function to print the greeting, then call it multiple times

B. Write the greeting message many times in the code

C. Use variables to store the greeting but write console.log many times

D. Write the greeting inside a comment and copy it when needed

Solution

1. Step 1: Understand the problem of repeating code

   Writing the same message many times makes code long and hard to change.

2. Step 2: Use functions to avoid repetition

   Functions let you write the message once and call it many times, making code cleaner.

3. Final Answer:

   Use a function to print the greeting, then call it multiple times -> Option A

4. Quick Check:

   Functions help reuse code = A [OK]

Hint: Use functions to avoid repeating code [OK]

Common Mistakes:

• Repeating code instead of using functions
• Using comments instead of code
• Misusing variables without functions