String concatenation in output in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the greeting message.

Javascript

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

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

A123

B'name'

Cname

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the variable name, which prints the word instead of its value.

We use the variable name without quotes to concatenate its value.

2fill in blank

medium

Complete the code to join first and last names with a space.

Javascript

let fullName = firstName + [1] + lastName;

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

A' '

B""

C'-'

D'_'

Attempts:

3 left

💡 Hint

Common Mistakes

Using no space or wrong separator characters like underscore or dash.

A space character inside quotes is used to separate the names.

3fill in blank

hard

Fix the error in concatenating number and string.

Javascript

let message = 'You have ' + [1] + ' new messages.';

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

AmessageCount

B'5'

C5

Dfive

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string literal '5' instead of the variable holding the count.

Use the variable messageCount which holds the number value to concatenate properly.

4fill in blank

hard

Fill both blanks to create a sentence with age and city.

Javascript

let info = 'I am ' + [1] + ' years old and live in ' + [2] + '.';

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

Aage

B'age'

Ccity

D'city'

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around variable names, which prints the names instead of values.

Use variables age and city without quotes to insert their values.

5fill in blank

hard

Fill all three blanks to build a full greeting sentence.

Javascript

let greeting = 'Hello, ' + [1] + '! You are ' + [2] + ' years old and from ' + [3] + '.';

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

AuserName

BuserAge

CuserCity

D'userName'

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around variable names, causing incorrect output.

Use variables userName, userAge, and userCity without quotes to get their values.

Practice

1. What does the + operator do when used between two strings in JavaScript?

easy

A. Divides the first string by the second

B. Joins the two strings together into one string

C. Multiplies the two strings

D. Subtracts the second string from the first

Solution

1. Step 1: Understand the + operator with strings

   In JavaScript, the + operator combines two strings into one continuous string.

2. Step 2: Recognize string concatenation

   When you write "Hello" + " World", it becomes "Hello World".

3. Final Answer:

   Joins the two strings together into one string -> Option B

4. Quick Check:

   String + String = Concatenation [OK]

Hint: Remember + joins strings like glue [OK]

Common Mistakes:

• Thinking + subtracts or divides strings
• Confusing + with arithmetic on strings
• Forgetting to add spaces inside quotes

2. Which of the following is the correct way to concatenate the strings "Hello" and "World" with a space between them in JavaScript?

easy

A. "Hello" - " " - "World"

B. "Hello" + "World"

C. "Hello" + " " + "World"

D. "Hello" * "World"

Solution

1. Step 1: Identify how to add space between words

   To add a space, include " " (space inside quotes) between the two strings.

2. Step 2: Use + operator to join all parts

   Use + to join "Hello", " ", and "World" to get "Hello World".

3. Final Answer:

   "Hello" + " " + "World" -> Option C

4. Quick Check:

   Use + and " " for spaces [OK]

Hint: Add spaces inside quotes when joining words [OK]

Common Mistakes:

• Forgetting the space string " "
• Using - or * instead of +
• Not putting quotes around the space

3. What will be the output of the following code?

let name = "Anna";
console.log("Hello, " + name + "!");

medium

A. Hello, + name + !

B. Hello, name!

C. Hello Anna

D. Hello, Anna!

Solution

1. Step 1: Understand variable substitution in concatenation

   The variable name holds the string "Anna" and is concatenated with other strings.

2. Step 2: Combine strings and variable value

   "Hello, " + name + "!" becomes "Hello, Anna!" when printed.

3. Final Answer:

   Hello, Anna! -> Option D

4. Quick Check:

   Variable value joins strings correctly [OK]

Hint: Variables inside + join as their values [OK]

Common Mistakes:

• Printing variable name instead of value
• Missing punctuation or spaces
• Using commas instead of + for concatenation

4. Find the error in this code snippet:

let greeting = "Hi";
let name = "Sam";
console.log(greeting + name);

What is missing if the output should be Hi Sam?

medium

A. A space string between greeting and name

B. Quotes around the variable name

C. A comma instead of + operator

D. Semicolon after console.log

Solution

1. Step 1: Check the concatenation result

   Currently, greeting + name joins "Hi" and "Sam" without space, resulting in "HiSam".

2. Step 2: Add a space string between variables

   Insert " " between greeting and name: greeting + " " + name to get "Hi Sam".

3. Final Answer:

   A space string between greeting and name -> Option A

4. Quick Check:

   Add " " to separate words [OK]

Hint: Add " " between words to separate them [OK]

Common Mistakes:

• Forgetting spaces in concatenation
• Using commas instead of +
• Thinking semicolon affects output

5. You want to create a greeting message that says Hello, John Doe! You have 5 new messages. using variables firstName, lastName, and messageCount. Which code correctly concatenates these values with spaces and punctuation?

hard

A. console.log("Hello, " + firstName + " " + lastName + "! You have " + messageCount + " new messages.");

B. console.log("Hello, " + firstName + lastName + "! You have " + messageCount + " new messages.");

C. console.log("Hello, " + firstName + " " + lastName + "! You have " + messageCount + "new messages.");

D. console.log("Hello, " + firstName + " " + lastName + "! You have " + messageCount + " new messages")

Solution

1. Step 1: Check spacing between first and last names

   console.log("Hello, " + firstName + " " + lastName + "! You have " + messageCount + " new messages."); adds a space string " " between firstName and lastName, correctly spacing the full name.

2. Step 2: Verify punctuation and spaces in message

   console.log("Hello, " + firstName + " " + lastName + "! You have " + messageCount + " new messages."); includes "! You have " and " new messages." with correct spaces and punctuation.

3. Final Answer:

   console.log("Hello, " + firstName + " " + lastName + "! You have " + messageCount + " new messages."); -> Option A

4. Quick Check:

   Use " " to separate names and punctuation correctly [OK]

Hint: Add spaces inside quotes between variables [OK]

Common Mistakes:

• Missing space between first and last name
• Missing space before 'new messages'
• Omitting punctuation at the end