Sass in Modern Frontend

Recently, I found a project that implemented the methodology mentioned in the famous book Atomic Habit by James Clear; I managed to update all the packages to the newest to get it up and running.

Honestly, switching from vue-cli to vite is pretty smooth since syntaxes didn’t change much within a big version. However, I encountered several errors related to Bootstrap and Sass.

The Sass official indicated that @import rule will be deprecated in the near future; that means we need to work with @use and @forward in our projects. So what are the at-rules of @use and @forward, then?

@use

We all deal with ES6-standard modules and exports every day. Imagine there are several modules such as “colors”, “fonts”, and “mixins.” Define them all starting with an underscore like _colors.scss.

// ./src/scss/colors.scss
$primary-color: #38f;
$secondary-color: #eee;
$flat-black: #333;

How to use it?

In another file, typically the one you would love to linked in the inedx.html. A @use "colors" will load all the members defined in this stylesheet module. But we cannot use it directly; a namespace prefix is needed when you trying to access them. It’s the module name by default; you can rename it using the “as” keyword.

Members mean “mixins”, “variables” and “functions” in SASS language.

// ./src/scss/styles.scss
@use "./variables/colors" as c;
body{
 background-color: c.$secondary-color;
}

Similarly, it’s pretty easy to include other modules:

// ./src/scss/styles.scss
@use "card";
@use "colors" as c;
@use "variables/fonts"; // equals to `@use "variables/fonts" as fonts`

$transition:all 0.5s ease-in-out;

body{
  font-size:fonts.$font-size;
  background-color: c.$secondary-color;
}
h1{
 color:c.$primary-color;
}

You can make this process even simple by assigning namespace to * .

@use "colors" as *;

h1{
 color:$primary-color;
}

Notice:

• A stylesheet’s @use rules must come before any rules other than @forward, including style rules.
• @use only ever loads each file once.
• Variables imported by @use can be overridden and take effect in all modules. You can set the initial value by adding a !default flag anywhere.

@forward

@forward rule will load all the variables, mixins and functions in a Sass stylesheet available when you load it in another stylesheet via @use .

The typical scenario will be manage different modules inside a folder and import them once for all in another stylesheet.

Lets say we have two modules colors and fonts in the following path.

// ./src/scss/variables/_fonts.scss
$font-size:1.5rem;
$font-weight:bold;

// ./src/scss/variables/_fonts.scss
$primary-color: #38f;
$secondary-color: #eee;
$flat-black: #333;

Then we create a new file under variables folder names _index.scss, by using @forward rule, the members inside previous two modules will be loaded when you using @use.

// ./src/scss/variables/_index.scss
@forward "colors";
@forward "fonts";

@use "card";
@use "mixins" as *;
@use "./variables" as v;

$transition:all 0.5s ease-in-out;

body{
  font-size:v.$font-size;
  background-color: v.$secondary-color;
}
h1{
 color:v.$primary-color;
}

Equals to:

@use "card";
@use "mixins" as *;
@use "./variables" as *;

$transition:all 0.5s ease-in-out;

body{
  font-size:$font-size;
  background-color: $secondary-color;
}
h1{
 color:v.$primary-color;
}

Those members aren’t available in your module, though. If you try to use variables loaded by @forward , something bad will happen.

@forward "colors";
@forward "fonts";

.box{
 color: colors.$color-primary;
 font-family: fonts.$font-primary;
}
// ERROR: There is no module with the namespace "colors"

Work with Vue3+Vite

We can still add preprocessor options in the vite.config.js setting to inject extra code in the target language for each style content.

https://github.com/vitejs/vite/issues/832

// vite.config.js
export default defineConfig({
    ...,
     css: {
  preprocessorOptions: {
    scss: {
      additionalData: `@use "@/assets/scss/global" as *;`,
    },
  },
 },
})

// /src/assets/scss/_variables.scss
$color-primary: #0074d9;
$color-secondary: #7fdbff;
$color-tertiary: #39cccc;

The global module will load all its members and memebers in variables and mixins when using @use.

// /src/assets/scss/_global.scss
@forward "variables";
@forward "mixins";

$font-roboto: "Roboto", sans-serif;

Since we removed the namespace eventually, we can use all the members from these modules directly in any component we want:

<script setup>
 ...
</script>

<template>
  ...
</template>

<style lang="scss" scoped >
h1{
 color:$color-primary;
    font-family: $font-roboto;
}
</style>