@import to @use migration in SASS

Introduction

We switch from @import to @use in Sass to organize styles better and avoid repeating code. @use helps keep things clear and safe.

When you want to include styles from another file without repeating variables or mixins.

When you want to avoid conflicts from loading the same file multiple times.

When you want to keep your styles modular and easier to maintain.

When you want to use namespaces to clearly see where styles come from.

When you want faster and safer Sass builds.

Syntax

SASS

@use 'filename' [as namespace];

@use loads a Sass file once and gives you access to its variables, mixins, and functions.

You can add a namespace to keep things organized, like @use 'colors' as c;.

Examples

Loads the colors.scss file with default namespace colors.

SASS

@use 'colors';

Loads colors.scss but uses c as a short namespace.

SASS

@use 'colors' as c;

Loads mixins.scss and makes its contents available without a namespace.

SASS

@use 'mixins' as *;

Sample Program

This example shows how to use variables and mixins from a colors.scss file using @use with a namespace c. It styles a button with colors and rounded corners.

SASS

@use 'colors' as c;

.button {
  background-color: c.$primary-color;
  color: c.$text-color;
  @include c.rounded-corners;
}

Important Notes

@import loads files multiple times and can cause conflicts; @use loads once.

Always use namespaces with @use to avoid name clashes, unless you use as *.

Update your old @import files gradually to @use for better Sass code.

Summary

@use replaces @import for safer and clearer Sass code.

It loads files once and uses namespaces to organize styles.

Use @use 'filename' as ns; to access variables and mixins with ns. prefix.

Practice

1. What is the main advantage of using @use instead of @import in Sass?

easy

A. It allows importing CSS files directly without processing.

B. It loads files only once and uses namespaces to avoid conflicts.

C. It automatically compiles Sass to CSS without a compiler.

D. It enables inline JavaScript execution inside Sass files.

Solution

1. Step 1: Understand @import behavior

   @import loads files multiple times and merges all variables globally, which can cause conflicts.

2. Step 2: Understand @use improvements

   @use loads files only once and requires a namespace prefix, preventing variable and mixin conflicts.

3. Final Answer:

   It loads files only once and uses namespaces to avoid conflicts. -> Option B

4. Quick Check:

   @use = safer, namespaced imports [OK]

Hint: Remember: @use loads once with namespaces [OK]

Common Mistakes:

• Thinking @use imports CSS files directly
• Assuming @use runs JavaScript
• Believing @use compiles Sass automatically

2. Which of the following is the correct syntax to replace @import 'colors'; with @use and a namespace c?

easy

A. @use 'colors' as c;

B. @use colors as 'c';

C. @use 'colors' namespace c;

D. @use 'colors' with c;

Solution

1. Step 1: Recall @use syntax

   The correct syntax is @use 'filename' as namespace; with quotes around filename and as keyword.

2. Step 2: Match options

   @use 'colors' as c; matches the correct syntax exactly: @use 'colors' as c;.

3. Final Answer:

   @use 'colors' as c; -> Option A

4. Quick Check:

   Correct @use syntax = @use 'colors' as c; [OK]

Hint: Use quotes and 'as' keyword for namespace [OK]

Common Mistakes:

• Omitting quotes around filename
• Using 'namespace' instead of 'as'
• Placing namespace inside quotes

3. Given the Sass files:

// _variables.scss
$primary-color: blue;

// styles.scss
@use 'variables' as vars;
.button {
  color: vars.$primary-color;
}

What color will the button text be in the compiled CSS?

medium

A. blue

B. vars.$primary-color

C. undefined

D. red

Solution

1. Step 1: Understand variable access with @use

   The variable $primary-color is accessed with the namespace prefix vars.$primary-color.

2. Step 2: Check variable value

   In _variables.scss, $primary-color is set to blue, so the button color will be blue.

3. Final Answer:

   blue -> Option A

4. Quick Check:

   Namespace prefix accesses variable value correctly [OK]

Hint: Use namespace prefix to get variable value [OK]

Common Mistakes:

• Using variable without namespace prefix
• Expecting variable name as string output
• Assuming default color red

4. What is wrong with this Sass code after migrating from @import to @use?

@use 'mixins';
.button {
  @include border-radius(5px);
}

medium

A. Cannot use @include with @use.

B. Incorrect quotes around filename in @use.

C. Missing namespace prefix before border-radius mixin.

D. Mixin name should be borderRadius instead.

Solution

1. Step 1: Understand @use namespace requirement

   When using @use, all variables and mixins must be accessed with the namespace prefix unless configured otherwise.

2. Step 2: Identify missing prefix

   The code calls @include border-radius(5px); without prefix. It should be @include mixins.border-radius(5px);.

3. Final Answer:

   Missing namespace prefix before border-radius mixin. -> Option C

4. Quick Check:

   @use requires namespace prefix [OK]

Hint: Add namespace prefix to mixin calls [OK]

Common Mistakes:

• Calling mixins without namespace prefix
• Confusing quotes usage in @use
• Thinking @include is disallowed

5. You have two Sass files:

// _colors.scss
$primary: red;

// _theme.scss
@use 'colors' as c;
$primary: blue !default;

// styles.scss
@use 'theme' as t;
.button {
  color: t.$primary;
}

What color will the button text be and why?

hard

A. blue, because $primary in theme overrides colors with !default.

B. blue, because @use merges variables without namespaces.

C. red, because !default prevents override in theme.

D. red, because $primary in colors overrides !default in theme.

Solution

1. Step 1: Understand !default behavior

   The !default flag sets a variable only if it is not already set.

2. Step 2: Analyze variable values

   $primary in colors is red. In theme, $primary is set to blue !default, so it will only be set if $primary was not already set.

3. Step 3: Check namespaces and usage

   theme uses colors as c, so $primary from colors is already set. Therefore, blue !default does not override red.

4. Final Answer:

   red, because $primary in colors overrides !default in theme. -> Option D

5. Quick Check:

   !default only sets if variable is unset, so red stays [OK]

Hint: Remember !default sets only if variable is unset [OK]

Common Mistakes:

• Assuming !default always overrides
• Ignoring namespaces in variable access
• Thinking variables merge without prefixes