@if conditional logic in SASS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the @if directive do in Sass?

The @if directive lets you write conditional code in Sass. It runs certain styles only if a condition is true.

beginner

How do you write an @if statement in Sass?

You write @if (condition) { /* styles here */ }. The styles inside run only if the condition is true.

beginner

Can you use @else with @if in Sass? What does it do?

Yes. @else runs styles if the @if condition is false. It helps handle two cases clearly.

beginner

Example: What will this Sass code output?

@if 5 > 3 { color: blue; }

Since 5 is greater than 3, the condition is true. The output CSS will be:

color: blue;

intermediate

Why use @if in Sass instead of plain CSS?

CSS alone can't do conditions. Sass @if lets you write smarter styles that change based on variables or logic, saving time and code.

What happens if the @if condition is false and there is no @else?

A The styles inside <code>@if</code> are skipped.

B The styles inside <code>@if</code> run anyway.

C Sass throws an error.

D The styles inside <code>@if</code> run twice.

If the condition is false and no @else is provided, Sass skips the styles inside the @if block.

Which of these is a valid Sass @if condition?

A @if (5 > 3) { ... }

B @if color = blue { ... }

C @if (color == blue) { ... }

D @if (font-size > 12px) { ... }

Sass supports numeric comparisons like 5 > 3. Option C is invalid because 'color' is undefined (though == is valid for equality), B uses = which is assignment, and D compares undefined 'font-size'.

What keyword do you use to add a fallback style if @if condition is false?

A @elseif

B @else

C @otherwise

D @fallback

@else runs styles when the @if condition is false.

Can you nest @if statements inside each other in Sass?

A No, nesting is not allowed.

B Only one level of nesting is allowed.

C Yes, nesting <code>@if</code> is allowed.

D Only with <code>@else</code>.

Sass allows nesting @if statements inside each other for complex conditions.

What will this Sass code output?

$size: 10px; @if $size > 5px { font-size: $size; }

A Error because of wrong syntax.

B No output because variables can't be compared.

C font-size: 5px;

D font-size: 10px;

The variable $size is 10px, which is greater than 5px, so the condition is true and outputs font-size: 10px;.

Explain how the @if directive works in Sass and give a simple example.

Think about how you decide to do something only if a condition is met.

Describe the difference between @if and @else in Sass conditional logic.

Consider how you choose between two options based on a yes/no question.

Practice

1. What does the @if directive do in Sass?

easy

A. It defines a variable.

B. It loops through a list of items.

C. It imports other Sass files.

D. It applies styles only if a condition is true.

Solution

1. Step 1: Understand the purpose of @if

   The @if directive checks a condition and applies styles only when that condition is true.

2. Step 2: Compare with other options

   Looping is done with @for or @each, importing with @import, and variables are defined with $.

3. Final Answer:

   It applies styles only if a condition is true. -> Option D

4. Quick Check:

   @if = conditional style application [OK]

Hint: Remember: @if controls styles by conditions [OK]

Common Mistakes:

• Confusing @if with loops or imports
• Thinking @if defines variables
• Assuming @if always runs styles

2. Which of the following is the correct syntax for using @if in Sass?

easy

A. @if $color == red { color: red; }

B. @if ($color = red) { color: red; }

C. @if $color === red { color: red; }

D. @if $color => red { color: red; }

Solution

1. Step 1: Check the correct comparison operator

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

2. Step 2: Verify syntax structure

   The correct syntax is @if $variable == value { ... } without parentheses around the condition.

3. Final Answer:

   @if $color == red { color: red; } -> Option A

4. Quick Check:

   Use == for comparison in @if [OK]

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

Common Mistakes:

• Using single equals (=) instead of double (==)
• Adding parentheses around condition
• Using JavaScript style === or =>

3. What will be the output CSS of this Sass code?

$theme: dark;

body {
  @if $theme == light {
    background: white;
    color: black;
  } @else if $theme == dark {
    background: black;
    color: white;
  } @else {
    background: gray;
    color: black;
  }
}

medium

A. body { background: black; color: white; }

B. body { background: white; color: black; }

C. body { background: gray; color: black; }

D. No output due to syntax error

Solution

1. Step 1: Check the value of $theme

   The variable $theme is set to dark.

2. Step 2: Evaluate the @if conditions

   The first condition $theme == light is false, so it skips to @else if $theme == dark, which is true. So it applies background: black; and color: white;.

3. Final Answer:

   body { background: black; color: white; } -> Option A

4. Quick Check:

   $theme = dark triggers @else if dark block [OK]

Hint: Match variable value to @if conditions carefully [OK]

Common Mistakes:

• Choosing first @if block without checking variable
• Ignoring @else if and @else blocks
• Assuming syntax error without checking carefully

4. Identify the error in this Sass code:

$size: 10px;

.box {
  @if $size > 5 {
    width: $size;
  } @else if $size < 5 {
    width: 5px;
  }
}

medium

A. Missing @else block for equal size case.

B. Units like px cannot be compared directly in @if.

C. Comparison operators like > and < are not allowed in @if.

D. Variable $size should be declared inside the block.

Solution

1. Step 1: Understand unit comparison in Sass

   Sass does not allow direct comparison of values with units like 10px > 5 in @if conditions.

2. Step 2: Check other options

   Comparison operators are allowed, @else block is optional, and variables can be declared outside blocks.

3. Final Answer:

   Units like px cannot be compared directly in @if. -> Option B

4. Quick Check:

   Cannot compare px units directly in @if [OK]

Hint: Avoid comparing units directly; use numbers or functions [OK]

Common Mistakes:

• Thinking > and < are invalid operators
• Assuming @else is mandatory
• Declaring variables only inside blocks

5. You want to set a button's background color based on a variable $status that can be 'success', 'warning', or 'error'. Which Sass code correctly uses @if conditional logic to apply green for success, yellow for warning, and red for error, with a default gray if none match?

hard

A. @if $status = success {
background: green;
} @else if $status == warning {
background: yellow;
} @else if $status == error {
background: red;
} @else {
background: gray;
}

B. @if $status = 'success' {
background: green;
} @else if $status = 'warning' {
background: yellow;
} @else if $status = 'error' {
background: red;
} @else {
background: gray;
}

C. @if $status == 'success' {
background: green;
} @else if $status == 'warning' {
background: yellow;
} @else if $status == 'error' {
background: red;
} @else {
background: gray;
}

D. @if $status === 'success' {
background: green;
} @else if $status === 'warning' {
background: yellow;
} @else if $status === 'error' {
background: red;
} @else {
background: gray;
}

Solution

1. Step 1: Check string comparison syntax

   In Sass, string values must be quoted and compared with ==, not = or ===.

2. Step 2: Verify the use of quotes around strings

   Options A and B miss quotes or use wrong operators; @if $status === 'success' { background: green; } @else if $status === 'warning' { background: yellow; } @else if $status === 'error' { background: red; } @else { background: gray; } uses === which is invalid in Sass.

3. Final Answer:

   @if $status == 'success' { background: green; } @else if $status == 'warning' { background: yellow; } @else if $status == 'error' { background: red; } @else { background: gray; } -> Option C

4. Quick Check:

   Use == and quotes for string comparison in @if [OK]

Hint: Compare strings with == and quotes in @if [OK]

Common Mistakes:

• Using single equals (=) instead of double (==)
• Omitting quotes around strings
• Using JavaScript style === operator