Basic input concepts (prompt overview) in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to ask the user for their name using prompt.

Javascript

const name = [1]('What is your name?');

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

Aconsole.log

Balert

Cprompt

Dconfirm

Attempts:

3 left

💡 Hint

Common Mistakes

Using alert instead of prompt

Using console.log instead of prompt

The prompt function shows a dialog box asking the user for input.

2fill in blank

medium

Complete the code to convert the input string to a number.

Javascript

const age = Number([1]);

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

AageInput

Bprompt('Enter your age')

C'30'

DparseInt('25')

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable that is not defined

Passing a string literal instead of prompt

The prompt function returns a string. Wrapping it with Number() converts it to a number.

3fill in blank

hard

Fix the error in the code to correctly store user input in a variable.

Javascript

let city;
city = [1]('Enter your city');

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

Aprompt

Balert

Cconsole.log

Dconfirm

Attempts:

3 left

💡 Hint

Common Mistakes

Using alert or confirm instead of prompt

Trying to assign console.log output

Use prompt to get input from the user and assign it to the variable.

4fill in blank

hard

Fill both blanks to ask for a number and convert it to an integer.

Javascript

const input = [1]('Enter a number');
const number = [2](input);

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

Aprompt

BparseInt

CNumber

Dalert

Attempts:

3 left

💡 Hint

Common Mistakes

Using alert instead of prompt

Using Number instead of parseInt when integer is needed

First, use prompt to get input as a string. Then use parseInt to convert it to an integer.

5fill in blank

hard

Fill all three blanks to get user input, convert to number, and check if it is positive.

Javascript

const input = [1]('Enter a number');
const num = [2](input);
const isPositive = num [3] 0;

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

Aprompt

BNumber

C>

DparseInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using parseInt instead of Number for conversion

Using < instead of > for comparison

Use prompt to get input, Number to convert it, and > to check if positive.

Practice

1. What does the prompt() function do in JavaScript?

easy

A. It displays a message in the console.

B. It pauses the program without any input.

C. It creates a new HTML element.

D. It asks the user to enter some input as text.

Solution

1. Step 1: Understand the purpose of prompt()

   The prompt() function shows a dialog box that asks the user to type something.

2. Step 2: Identify the type of input it collects

   The input collected is always text (a string), even if the user types numbers.

3. Final Answer:

   It asks the user to enter some input as text. -> Option D

4. Quick Check:

   prompt() = asks user input [OK]

Hint: Remember prompt() always asks user for text input [OK]

Common Mistakes:

• Thinking prompt() shows output instead of input
• Assuming prompt() returns numbers automatically
• Confusing prompt() with console.log()

2. Which of the following is the correct syntax to ask the user for their name using prompt()?

easy

A. let name = prompt('Enter your name');

B. prompt = 'Enter your name';

C. let name = input('Enter your name');

D. console.prompt('Enter your name');

Solution

1. Step 1: Check the correct function name and usage

   The function to get input is prompt(), not input() or console.prompt().

2. Step 2: Assign the result to a variable

   We store the user's input in a variable using let name = prompt('Enter your name');.

3. Final Answer:

   let name = prompt('Enter your name'); -> Option A

4. Quick Check:

   Correct prompt syntax = let name = prompt('Enter your name'); [OK]

Hint: Use let variable = prompt('message') to get input [OK]

Common Mistakes:

• Using input() instead of prompt()
• Trying to assign prompt as a string
• Using console.prompt() which doesn't exist

3. What will be the output of this code if the user enters 25 in the prompt?

let age = prompt('Enter your age');
console.log(typeof age);

medium

A. "string"

B. "number"

C. "undefined"

D. "object"

Solution

1. Step 1: Understand the type returned by prompt()

   The prompt() function always returns a string, even if the user types a number.

2. Step 2: Check the output of typeof age

   Since age holds a string, typeof age will be "string".

3. Final Answer:

   "string" -> Option A

4. Quick Check:

   prompt() returns string type [OK]

Hint: prompt() always returns string type, not number [OK]

Common Mistakes:

• Assuming prompt returns a number automatically
• Confusing typeof output with input value
• Expecting undefined or object type

4. Identify the error in this code snippet:

let number = prompt('Enter a number');
let result = number + 10;
console.log(result);

medium

A. The prompt() function is missing parentheses.

B. The input from prompt() is a string, so adding 10 concatenates instead of sums.

C. The variable 'number' is not declared.

D. console.log() cannot print variables.

Solution

1. Step 1: Check the type of input from prompt()

   The prompt() returns a string, so number is a string.

2. Step 2: Understand the effect of adding a number to a string

   Adding 10 to a string causes string concatenation, not numeric addition.

3. Final Answer:

   The input from prompt() is a string, so adding 10 concatenates instead of sums. -> Option B

4. Quick Check:

   String + number = concatenation [OK]

Hint: Convert prompt input to number before adding [OK]

Common Mistakes:

• Thinking prompt input is a number by default
• Ignoring type conversion before arithmetic
• Believing console.log can't print variables

5. How can you correctly get a number from the user using prompt() and add 10 to it? Choose the correct code.

hard

A. let num = prompt('Enter number') + 10;

B. let num = parseInt(prompt); num + 10;

C. let num = Number(prompt('Enter number')) + 10;

D. let num = prompt('Enter number'); num = num + 10;

Solution

1. Step 1: Convert prompt input to a number

   Use Number() or parseInt() to convert the string input to a number.

2. Step 2: Add 10 to the converted number

   After conversion, adding 10 performs numeric addition correctly.

3. Final Answer:

   let num = Number(prompt('Enter number')) + 10; -> Option C

4. Quick Check:

   Convert input to number before adding [OK]

Hint: Wrap prompt() with Number() to convert input [OK]

Common Mistakes:

• Adding number directly to prompt() string
• Forgetting to call prompt() as a function
• Using parseInt without parentheses