Compiling Multiple CSS Files into One

Stu Robson is on a mission to “un-Sass” his CSS. I see articles like this pop up every year, and for good reason as CSS has grown so many new legs in recent years. So much so that much of the core features that may have prompted you to reach for Sass in the past are now baked directly into CSS. In fact, we have Jeff Bridgforth on tap with a related article next week.

What I like about Stu’s stab at this is that it’s an ongoing journey rather than a wholesale switch. In fact, he’s out with a new post that pokes specifically at compiling multiple CSS files into a single file. Splitting and organizing styles into separate files is definitely the reason I continue to Sass-ify my work. I love being able to find exactly what I need in a specific file and updating it without having to dig through a monolith of style rules.

But is that a real reason to keep using Sass? I’ve honestly never questioned it, perhaps due to a lizard brain that doesn’t care as long as something continues to work. Oh, I want partialized style files? Always done that with a Sass-y toolchain that hasn’t let me down yet. I know, not the most proactive path.

Stu outlines two ways to compile multiple CSS files when you aren’t relying on Sass for it:

Using PostCSS

Ah, that’s right, we can use PostCSS both with and without Sass. It’s easy to forget that PostCSS and Sass are compatible, but not dependent on one another.

postcss main.css -o output.css

Stu explains why this could be a nice way to toe-dip into un-Sass’ing your work:

PostCSS can seamlessly integrate with popular build tools like webpack, Gulp, and Rollup, allowing you to incorporate CSS compilation into your existing development workflow without potential, additional configuration headaches.

Custom Script for Compilation

The ultimate thing would be eliminating the need for any dependencies. Stu has a custom Node.js script for that:

const fs = require('fs');
const path = require('path');
// Function to read and compile CSS
function compileCSS(inputFile, outputFile) {
    const cssContent = fs.readFileSync(inputFile, 'utf-8');
    const imports = cssContent.match(/@import\s+['"]([^'"]+)['"]/g) || [];
    let compiledCSS = '';
    // Read and append each imported CSS file
    imports.forEach(importStatement => {
        const filePath = importStatement.match(/['"]([^'"]+)['"]/)[1];
        const fullPath = path.resolve(path.dirname(inputFile), filePath);
        compiledCSS += fs.readFileSync(fullPath, 'utf-8') + '\n';
    });
    // Write the compiled CSS to the output file
    fs.writeFileSync(outputFile, compiledCSS.trim());
    console.log(`Compiled CSS written to ${outputFile}`);
}
// Usage
const inputCSSFile = 'index.css'; // Your main CSS file
const outputCSSFile = 'output.css'; // Output file
compileCSS(inputCSSFile, outputCSSFile);

Not 100% free of dependencies, but geez, what a nice way to reduce the overhead and still combine files:

node compile-css.js

This approach is designed for a flat file directory. If you’re like me and prefer nested subfolders:

With the flat file structure and single-level import strategy I employ, nested imports (you can do with postcss-import aren’t necessary for my project setup, simplifying the compilation process while maintaining clean organisation.

Very cool, thanks Stu! And check out the full post because there’s a lot of helpful context behind this, particularly with the custom script.

Compiling Multiple CSS Files into One originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.