Conditional mixins with @if in SASS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a mixin that applies a background color only if the condition is true.

SASS

@mixin bg-color($color, $apply) {
  @if [1] {
    background-color: $color;
  }
}

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

A$apply == true

B$color == red

C$apply = true

D$color != null

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single '=' instead of '==' for comparison.

Checking the wrong variable in the condition.

The mixin uses @if to check if $apply is true before applying the background color.

2fill in blank

medium

Complete the code to include a font size only if the size is greater than 0.

SASS

@mixin font-size($size) {
  @if [1] {
    font-size: $size;
  }
}

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

A$size < 0

B$size == 0

C$size != 0

D$size > 0

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in the condition.

Checking for equality with 0 instead of greater than 0.

The mixin applies font-size only if $size is greater than 0.

3fill in blank

hard

Fix the error in the mixin to correctly check if $enabled is true.

SASS

@mixin toggle($enabled) {
  @if [1] {
    display: block;
  } @else {
    display: none;
  }
}

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

A$enabled = true

B$enabled == true

C$enabled === true

Denabled == true

Attempts:

3 left

💡 Hint

Common Mistakes

Using single '=' which assigns instead of compares.

Omitting the '$' in variable name.

Use '==' to compare $enabled with true in Sass conditions.

4fill in blank

hard

Fill both blanks to create a mixin that sets padding only if $padding is not null and greater than 0.

SASS

@mixin set-padding($padding) {
  @if [1] and [2] {
    padding: $padding;
  }
}

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

A$padding != null

B$padding == null

C$padding > 0

D$padding < 0

Attempts:

3 left

💡 Hint

Common Mistakes

Checking if $padding is null instead of not null.

Using '<' instead of '>' for size comparison.

The mixin checks that $padding is not null and greater than 0 before applying padding.

5fill in blank

hard

Fill all three blanks to create a mixin that sets color only if $color is not null, $enabled is true, and $mode equals 'dark'.

SASS

@mixin set-color($color, $enabled, $mode) {
  @if [1] and [2] and [3] {
    color: $color;
  }
}

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

A$color != null

B$enabled == true

C$mode == 'dark'

D$mode != 'dark'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' for $mode comparison.

Omitting the '$' in variable names.

Using assignment '=' instead of comparison '=='.

The mixin applies color only if $color is set, $enabled is true, and $mode is 'dark'.

Practice

1. What does the @if directive inside a Sass mixin do?

easy

A. It imports another Sass file.

B. It loops through a list of values.

C. It defines a new CSS class.

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

Solution

1. Step 1: Understand the role of @if in Sass mixins

   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 uses @import, and defining classes is done with selectors, not @if.

3. Final Answer:

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

4. Quick Check:

   @if controls conditional style application [OK]

Hint: Remember: @if controls conditions inside mixins [OK]

Common Mistakes:

• Confusing @if with loops like @for or @each
• Thinking @if imports files
• Assuming @if creates CSS selectors

2. Which of the following is the correct syntax to use @if inside a Sass mixin?

easy

A. @mixin example($flag) { @if $flag { color: red; } }

B. @mixin example($flag) { if ($flag) { color: red; } }

C. @mixin example($flag) { @if ($flag) color: red; }

D. @mixin example($flag) { @if $flag: { color: red; } }

Solution

1. Step 1: Review correct @if syntax in Sass mixins

   The correct syntax uses @if followed by a condition without parentheses, then curly braces for the block: @if $flag { ... }.

2. Step 2: Check each option

   @mixin example($flag) { @if $flag { color: red; } } matches correct syntax. @mixin example($flag) { if ($flag) { color: red; } } misses @ before if. @mixin example($flag) { @if ($flag) color: red; } incorrectly uses parentheses and misses braces. @mixin example($flag) { @if $flag: { color: red; } } uses colon incorrectly.

3. Final Answer:

   @mixin example($flag) { @if $flag { color: red; } } -> Option A

4. Quick Check:

   Correct @if syntax = @mixin example($flag) { @if $flag { color: red; } } [OK]

Hint: Use @if without parentheses, with braces for blocks [OK]

Common Mistakes:

• Omitting @ before if
• Using parentheses around condition
• Using colon instead of braces

3. Given the Sass code:

@mixin color-choice($color) {
  @if $color == 'red' {
    color: red;
  } @else if $color == 'blue' {
    color: blue;
  } @else {
    color: black;
  }
}

.test {
  @include color-choice('blue');
}

What color will the .test class have?

medium

A. red

B. black

C. blue

D. no color applied

Solution

1. Step 1: Check the mixin call parameter

   The mixin is called with 'blue' as the argument for $color.

2. Step 2: Follow the conditional branches

   The first condition checks if $color == 'red' which is false. The second condition @else if $color == 'blue' is true, so color: blue; is applied.

3. Final Answer:

   blue -> Option C

4. Quick Check:

   Input 'blue' triggers blue color [OK]

Hint: Match input string exactly in @if conditions [OK]

Common Mistakes:

• Confusing single quotes with no quotes
• Ignoring @else if branch
• Assuming default else applies first

4. Identify the error in this Sass mixin:

@mixin size($value) {
  @if $value > 10
    font-size: 2rem;
  @else
    font-size: 1rem;
}

medium

A. Missing curly braces after @if and @else blocks

B. Incorrect comparison operator >

C. Mixin name cannot be 'size'

D. Variables cannot be used in @if conditions

Solution

1. Step 1: Check syntax for @if and @else blocks

   In Sass, when using @if and @else inside mixins, blocks must be wrapped in curly braces { }.

2. Step 2: Identify missing braces

   The code lacks braces after @if $value > 10 and @else, causing syntax errors.

3. Final Answer:

   Missing curly braces after @if and @else blocks -> Option A

4. Quick Check:

   Always use braces for conditional blocks [OK]

Hint: Always wrap @if/@else blocks in braces { } [OK]

Common Mistakes:

• Omitting braces for single-line blocks
• Using wrong comparison operators
• Thinking variable names are restricted

5. You want a mixin that sets background color based on a status: 'success' = green, 'warning' = yellow, 'error' = red, else gray. Which Sass mixin correctly uses @if to achieve this?

hard

A. @mixin status-bg($status) {
@if $status = 'success' {
background-color: green;
} @else if $status = 'warning' {
background-color: yellow;
} @else if $status = 'error' {
background-color: red;
} @else {
background-color: gray;
}
}

B. @mixin status-bg($status) {
@if $status == 'success' {
background-color: green;
} @else if $status == 'warning' {
background-color: yellow;
} @else if $status == 'error' {
background-color: red;
} @else {
background-color: gray;
}
}

C. @mixin status-bg($status) {
@if $status == success {
background-color: green;
} @else if $status == warning {
background-color: yellow;
} @else if $status == error {
background-color: red;
} @else {
background-color: gray;
}
}

D. @mixin status-bg($status) {
@if $status === 'success' {
background-color: green;
} @else if $status === 'warning' {
background-color: yellow;
} @else if $status === 'error' {
background-color: red;
} @else {
background-color: gray;
}
}

Solution

1. Step 1: Check comparison operators and string quotes

   Sass uses == for comparison and strings must be quoted. @mixin status-bg($status) { @if $status == 'success' { background-color: green; } @else if $status == 'warning' { background-color: yellow; } @else if $status == 'error' { background-color: red; } @else { background-color: gray; } } uses == and quotes correctly.

2. Step 2: Review other options for errors

   @mixin status-bg($status) { @if $status = 'success' { background-color: green; } @else if $status = 'warning' { background-color: yellow; } @else if $status = 'error' { background-color: red; } @else { background-color: gray; } } uses single = which is assignment, not comparison. @mixin status-bg($status) { @if $status == success { background-color: green; } @else if $status == warning { background-color: yellow; } @else if $status == error { background-color: red; } @else { background-color: gray; } } misses quotes around strings. @mixin status-bg($status) { @if $status === 'success' { background-color: green; } @else if $status === 'warning' { background-color: yellow; } @else if $status === 'error' { background-color: red; } @else { background-color: gray; } } uses === which is invalid in Sass.

3. Final Answer:

   @mixin status-bg($status) { @if $status == 'success' { background-color: green; } @else if $status == 'warning' { background-color: yellow; } @else if $status == 'error' { background-color: red; } @else { background-color: gray; } } -> Option B

4. Quick Check:

   Use == and quotes for string comparison in Sass [OK]

Hint: Use == and quotes for string checks in @if [OK]

Common Mistakes:

• Using = instead of == for comparison
• Omitting quotes around strings
• Using === which is invalid in Sass