Output formatting basics in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is output formatting in programming?

Output formatting means arranging and displaying data in a way that is easy to read and understand.

beginner

How do you print a variable with text in JavaScript using template literals?

Use backticks `` and ${variable} inside them. Example: console.log(`Hello, ${name}!`);

beginner

What does console.log() do in JavaScript?

It prints messages or values to the browser console or terminal, helping you see output or debug your code.

intermediate

How can you format numbers to show two decimal places in JavaScript?

Use the <code>toFixed(2)</code> method. Example: <code>let price = 5.6789; console.log(price.toFixed(2)); // 5.68</code>

beginner

Why is output formatting important?

It makes data clear and easy to understand, which helps users and developers avoid mistakes and confusion.

Which symbol is used to create template literals in JavaScript?

A Backticks (`)

B Single quotes (')

C Double quotes (")

D Parentheses ()

Template literals use backticks (`) to allow embedding variables easily.

What does console.log('Hello, ' + name); do?

A Prints 'Hello, ' followed by the value of name

B Creates a new variable called console

C Stops the program

D Formats a number

It prints the text 'Hello, ' plus the value stored in the variable name.

How do you limit a number to 2 decimal places in JavaScript?

A number.toString(2)

B number.toFixed(2)

C number.round(2)

D number.format(2)

The toFixed(2) method formats a number to 2 decimal places.

Which method prints output to the console in JavaScript?

A echo()

B print()

C console.log()

D write()

console.log() is the standard way to print output in JavaScript.

Why use output formatting?

A To delete data

B To slow down the program

C To hide errors

D To make output clear and readable

Formatting output helps users and developers understand data easily.

Explain how to use template literals in JavaScript to format output with variables.

Think about how to combine text and variables in one string.

Describe why formatting numbers to fixed decimal places is useful in output.

Consider how numbers look when printed to users.

Practice

1. What is the correct way to include a variable name inside a string using template literals in JavaScript?

easy

A. console.log(`Hello, ${name}!`);

B. console.log('Hello, ' + name + '!');

C. console.log("Hello, ${name}!");

D. console.log('Hello, ${name}!');

Solution

1. Step 1: Understand template literals syntax

   Template literals use backticks (`) and ${} to insert variables inside strings.

2. Step 2: Identify correct usage

   console.log(`Hello, ${name}!`); uses backticks and ${name} correctly to embed the variable.

3. Final Answer:

   console.log(`Hello, ${name}!`); -> Option A

4. Quick Check:

   Backticks + ${} = correct template literal [OK]

Hint: Use backticks and ${variable} for easy variable insertion [OK]

Common Mistakes:

• Using quotes instead of backticks for template literals
• Forgetting ${} around variable
• Using single or double quotes with ${} which won't interpolate

2. Which of the following is the correct syntax to print the number 5 and the word 'apples' in one line using template literals?

easy

A. console.log(`5 apples`);

B. console.log(`5 + apples`);

C. console.log('5 apples');

D. console.log(`5 ${apples}`);

Solution

1. Step 1: Check the use of template literals

   Backticks allow strings with variables inside ${}, but here no variable is needed.

2. Step 2: Identify correct string

   console.log(`5 apples`); correctly uses backticks with plain text '5 apples'.

3. Final Answer:

   console.log(`5 apples`); -> Option A

4. Quick Check:

   Backticks with plain text = valid string [OK]

Hint: Use backticks for strings even without variables [OK]

Common Mistakes:

• Using quotes instead of backticks when template literals expected
• Trying to insert undefined variable apples
• Adding plus sign inside template literal as text

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

const count = 3;
console.log(`You have ${count} new messages.`);

medium

A. You have ${count} new messages.

B. You have count new messages.

C. You have 3 new messages.

D. SyntaxError

Solution

1. Step 1: Understand template literal variable insertion

   The variable count inside ${} is replaced by its value 3.

2. Step 2: Evaluate the console.log output

   The string becomes 'You have 3 new messages.' and prints exactly that.

3. Final Answer:

   You have 3 new messages. -> Option C

4. Quick Check:

   Variable inside ${} = replaced by value [OK]

Hint: Variables inside ${} show their value in template strings [OK]

Common Mistakes:

• Thinking ${count} prints literally
• Confusing quotes and backticks
• Expecting variable name instead of value

4. Find the error in this code snippet:

let user = 'Anna';
console.log('Welcome, ${user}!');

medium

A. Missing semicolon after let declaration

B. Single quotes do not allow variable interpolation

C. Variable user is not declared

D. Backticks are missing around the string

Solution

1. Step 1: Check string quotes for interpolation

   Single quotes ('') do not process ${} as variable placeholders.

2. Step 2: Identify correct string type for template literals

   Backticks (`) are needed to enable variable interpolation.

3. Final Answer:

   Single quotes do not allow variable interpolation -> Option B

4. Quick Check:

   Use backticks for ${} interpolation [OK]

Hint: Use backticks, not single quotes, for ${} variables [OK]

Common Mistakes:

• Thinking single quotes support ${} interpolation
• Ignoring missing backticks
• Assuming variable is undeclared

5. You want to print a message showing a user's name and age using template literals. The variables are name = 'Sam' and age = 25. Which code correctly formats the output as:
Hello, Sam! You are 25 years old.

hard

A. console.log(`Hello, ${name}! You are age years old.`);

B. console.log('Hello, ' + name + '! You are ' + age + ' years old.');

C. console.log(`Hello, name! You are age years old.`);

D. console.log(`Hello, ${name}! You are ${age} years old.`);

Solution

1. Step 1: Use template literals with variables

   Backticks and ${} allow embedding variables name and age inside the string.

2. Step 2: Check each option for correct variable usage

   console.log(`Hello, ${name}! You are ${age} years old.`); correctly uses ${name} and ${age} to insert values.

3. Final Answer:

   console.log(`Hello, ${name}! You are ${age} years old.`); -> Option D

4. Quick Check:

   Backticks + ${var} for each variable = correct [OK]

Hint: Use ${variable} inside backticks for multiple variables [OK]

Common Mistakes:

• Using variable names without ${} inside template literals
• Mixing quotes and backticks incorrectly
• Concatenating strings instead of using template literals