What is JavaScript - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to display a message in the browser console.

Javascript

console.[1]('Hello, JavaScript!');

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

Awrite

Blog

Cprint

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using console.print or console.write which do not exist.

Trying to use alert instead of console.log.

The console.log function prints messages to the browser console.

2fill in blank

medium

Complete the code to declare a variable named name with the value 'Alice'.

Javascript

let [1] = 'Alice';

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

Aname

Blet

Cconst

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Putting 'var' or 'let' in the blank instead of the variable name.

Using a number or string instead of a variable name.

The variable name is name. The code declares it with let.

3fill in blank

hard

Fix the error in the code to correctly add two numbers and store the result.

Javascript

let sum = 5 [1] 3;

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using minus or multiplication instead of addition.

Leaving the operator blank.

The plus sign + adds two numbers together.

4fill in blank

hard

Fill both blanks to create an object with a property and access its value.

Javascript

const person = { [1]: 'Bob' };
console.log(person.[2]);

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

Aname

Bage

Dheight

Attempts:

3 left

💡 Hint

Common Mistakes

Using different property names for key and access.

Using properties that are not defined.

The object has a property name. Access it with person.name.

5fill in blank

hard

Fill all three blanks to create a function that returns the square of a number.

Javascript

function [1]([2]) {
  return [2] [3] [2];
}

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

Asquare

Bnum

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication.

Using different variable names inside the function.

The function named square takes num and returns num * num.

Practice

1. What is JavaScript primarily used for on websites?

easy

A. To write the webpage content

B. To style the webpage layout

C. To add actions and interactivity

D. To store data on the server

Solution

1. Step 1: Understand JavaScript's role

   JavaScript is a programming language that adds actions and interactivity to websites.

2. Step 2: Compare with other web technologies

   HTML writes content, CSS styles layout, and server stores data, so JavaScript adds interactivity.

3. Final Answer:

   To add actions and interactivity -> Option C

4. Quick Check:

   JavaScript = Interactivity [OK]

Hint: JavaScript makes websites interactive, not just static [OK]

Common Mistakes:

• Confusing JavaScript with CSS for styling
• Thinking JavaScript writes webpage text
• Assuming JavaScript stores server data

2. Which of the following is the correct way to include JavaScript in an HTML file?

easy

A. <link href='app.js'>

B. <script src='app.js'></script>

C. <js>app.js</js>

D. <style>app.js</style>

Solution

1. Step 1: Identify correct HTML tag for JavaScript

   The <script> tag is used to include JavaScript files or code in HTML.

2. Step 2: Check the options

   <script src='app.js'></script> uses <script src='app.js'></script>, which is correct syntax to include an external JS file.

3. Final Answer:

   <script src='app.js'></script> -> Option B

4. Quick Check:

   Use <script> for JavaScript [OK]

Hint: JavaScript files go inside <script> tags [OK]

Common Mistakes:

• Using <style> tag for JavaScript
• Using non-existent <js> tag
• Using <link> tag which is for CSS

3. What will the following JavaScript code output in the browser console?

console.log('Hello, ' + 'world!');

medium

A. Hello, world!

B. Hello, + world!

C. Hello world!

D. Error

Solution

1. Step 1: Understand string concatenation

   The + operator joins two strings into one continuous string.

2. Step 2: Combine the strings

   'Hello, ' + 'world!' becomes 'Hello, world!'. console.log prints this to the console.

3. Final Answer:

   Hello, world! -> Option A

4. Quick Check:

   String + String = Combined string [OK]

Hint: Plus (+) joins strings in JavaScript [OK]

Common Mistakes:

• Expecting plus sign to print
• Missing comma or space in output
• Thinking it causes an error

4. Find the error in this JavaScript code snippet:

function greet() {
  console.log('Hi there!')
}

medium

A. Missing semicolon after console.log statement

B. Missing parentheses in function declaration

C. Missing curly braces around function body

D. No error, code is correct

Solution

1. Step 1: Check function syntax

   The function greet() has parentheses and curly braces properly placed.

2. Step 2: Check statement termination

   JavaScript allows optional semicolons; missing semicolon here does not cause error.

3. Final Answer:

   No error, code is correct -> Option D

4. Quick Check:

   Semicolons optional in JS [OK]

Hint: Semicolons are optional in many JS cases [OK]

Common Mistakes:

• Thinking semicolon is always required
• Confusing function syntax rules
• Assuming missing semicolon causes error

5. You want to make a webpage respond when a user clicks a button. Which JavaScript concept should you use?

hard

A. Event handling

B. Variable declaration

C. CSS styling

D. HTML structuring

Solution

1. Step 1: Understand user interaction

   Responding to clicks means reacting to user events on the page.

2. Step 2: Identify JavaScript feature for user actions

   Event handling lets JavaScript listen and respond to user actions like clicks.

3. Final Answer:

   Event handling -> Option A

4. Quick Check:

   User clicks = Event handling [OK]

Hint: Use event handlers to react to user actions [OK]

Common Mistakes:

• Confusing CSS styling with interactivity
• Thinking variables handle clicks
• Assuming HTML alone manages user actions