Boolean values and logic in SASS - Practice Problems & Coding Challenges

Challenge - 5 Problems

📝 Syntax

intermediate

What is the output color of this Sass code?

Given the following Sass code, what color will the .box background be after compilation?

SASS

$is-active: true;
$has-error: false;

.box {
  background-color: if($is-active and not $has-error, green, red);
}

A green

B yellow

C blue

D red

💡 Hint

Remember that and requires both conditions to be true, and not reverses the boolean.

The variable $is-active is true and $has-error is false. The expression $is-active and not $has-error evaluates to true and true, which is true. So the if function returns green.

🧠 Conceptual

intermediate

Which Sass expression evaluates to false?

Select the Sass boolean expression that evaluates to false.

A $c: not false;

B $b: true or false;

C $a: true and false;

D $d: true and not false;

💡 Hint

Recall that and requires both sides to be true to return true.

true and false is false. The others evaluate to true.

❓ rendering

advanced

What color will the .alert box be?

Consider this Sass code. What color will the .alert background be after compiling to CSS?

SASS

$error: false;
$warning: true;

.alert {
  background-color: if($error or $warning, orange, blue);
}

A red

B blue

C green

D orange

💡 Hint

The or operator returns true if either side is true.

$error is false, but $warning is true. So $error or $warning is true, making the background color orange.

❓ selector

advanced

Which selector applies styles only when both conditions are true?

Given these Sass variables, which selector will apply styles only if $is-visible and $is-enabled are both true?

SASS

$is-visible: true;
$is-enabled: false;

// Choose the correct selector

A .component { @if $is-visible or $is-enabled { color: black; } }

B .component { @if $is-visible and $is-enabled { color: black; } }

C .component { @if not $is-visible and $is-enabled { color: black; } }

D .component { @if $is-visible and not $is-enabled { color: black; } }

💡 Hint

Remember and requires both to be true.

Option B applies styles only if both $is-visible and $is-enabled are true. The others apply styles under different conditions.

❓ accessibility

expert

How to use boolean logic in Sass to improve accessibility with focus styles?

You want to add a focus outline only if $is-accessible is true and $user-prefers-focus is true. Which Sass code snippet correctly applies this logic?

SASS

$is-accessible: true;
$user-prefers-focus: false;

.button {
  // Add focus outline conditionally
}

A

.button {
  @if $is-accessible and $user-prefers-focus {
    outline: 2px solid blue;
  }
}

B

.button {
  @if not $is-accessible and $user-prefers-focus {
    outline: 2px solid blue;
  }
}

C

.button {
  @if $is-accessible or $user-prefers-focus {
    outline: 2px solid blue;
  }
}

D

.button {
  @if $is-accessible and not $user-prefers-focus {
    outline: 2px solid blue;
  }
}

💡 Hint

Focus outlines should appear only when both accessibility and user preference are true.

Option A correctly uses and to require both $is-accessible and $user-prefers-focus to be true before applying the outline. The others apply the outline under incorrect conditions.

Practice

1. In Sass, which of the following represents a Boolean value?

easy

A. 1

B. "true"

C. "false"

D. true

Solution

1. Step 1: Understand Sass Boolean values

   In Sass, Boolean values are the keywords true and false, not strings or numbers.

2. Step 2: Identify the correct Boolean

   true uses true as a keyword, which is the correct Boolean value in Sass.

3. Final Answer:

   true -> Option D

4. Quick Check:

   Boolean values in Sass are true or false [OK]

Hint: Look for keywords true or false without quotes [OK]

Common Mistakes:

• Confusing strings "true" or "false" with Boolean values
• Using numbers like 1 or 0 as Booleans
• Thinking true/false must be quoted

2. Which of the following is the correct syntax to use a Boolean in an @if statement in Sass?

easy

A. @if $is-active == true { color: blue; }

B. @if $is-active = true { color: blue; }

C. @if $is-active === true { color: blue; }

D. @if $is-active != true { color: blue; }

Solution

1. Step 1: Check Sass comparison operator

   Sass uses == to compare values in @if statements, not = or ===.

2. Step 2: Identify correct syntax

   @if $is-active == true { color: blue; } uses == correctly to compare $is-active with true.

3. Final Answer:

   @if $is-active == true { color: blue; } -> Option A

4. Quick Check:

   Use double equals (==) for comparison in Sass [OK]

Hint: Use double equals (==) for comparisons in @if [OK]

Common Mistakes:

• Using single equals (=) which assigns instead of compares
• Using triple equals (===) which is invalid in Sass
• Using != when checking for true

3. What color will the following Sass code output?

$dark-mode: false;

body {
  @if $dark-mode {
    background-color: black;
  } @else {
    background-color: white;
  }
}

medium

A. white

B. black

C. transparent

D. red

Solution

1. Step 1: Check the Boolean value of $dark-mode

   $dark-mode is set to false, so the @if condition is false.

2. Step 2: Follow the @else branch

   Since the condition is false, the code inside @else runs, setting background-color to white.

3. Final Answer:

   white -> Option A

4. Quick Check:

   False condition triggers @else block [OK]

Hint: False triggers @else styles, not @if [OK]

Common Mistakes:

• Assuming false runs the @if block
• Confusing true/false values
• Ignoring the @else block

4. Identify the error in this Sass code:

$is-visible: true

.container {
  @if $is-visible == true {
    display: block;
  } @else {
    display: none;
  }
}

medium

A. Incorrect use of @else block

B. Wrong comparison operator in @if

C. Missing semicolon after variable declaration

D. Variable name cannot start with $

Solution

1. Step 1: Check variable declaration syntax

   In Sass, variable declarations must end with a semicolon. Here, $is-visible: true is missing a semicolon.

2. Step 2: Verify other syntax

   The comparison operator == and @else block are correct. Variable names can start with $.

3. Final Answer:

   Missing semicolon after variable declaration -> Option C

4. Quick Check:

   Variable declarations need semicolons [OK]

Hint: Check for missing semicolons after variables [OK]

Common Mistakes:

• Forgetting semicolon after variable assignment
• Confusing = and == in @if
• Thinking @else is optional syntax

5. You want to apply a red border only if both $is-error and $is-active are true in Sass. Which code correctly uses Boolean logic to do this?

hard

A. @if $is-error & $is-active { border: 1px solid red; }

B. @if $is-error and $is-active { border: 1px solid red; }

C. @if $is-error && $is-active { border: 1px solid red; }

D. @if $is-error or $is-active { border: 1px solid red; }

Solution

1. Step 1: Understand Sass Boolean operators

   Sass uses the keyword and for logical AND, not symbols like && or &.

2. Step 2: Identify correct syntax

   @if $is-error and $is-active { border: 1px solid red; } correctly uses and to check if both variables are true before applying the border.

3. Final Answer:

   @if $is-error and $is-active { border: 1px solid red; } -> Option B

4. Quick Check:

   Use and for logical AND in Sass [OK]

Hint: Use 'and' keyword for AND logic in Sass [OK]

Common Mistakes:

• Using && or & which are invalid in Sass
• Using 'or' instead of 'and' for both true
• Confusing bitwise & with logical and