A SASS vars loader for Webpack

Reads sass vars from Javascript files, from JSON files or from the Webpack config.

Install

npm install @epegzz/sass-vars-loader --save-dev

Usage

The example directory contains a fully functional example project.

It uses sass-vars-loader to inject vars into sass files in 3 different ways:

• via Javascript file
• via JSON file
• via webpack config

In the file app/styles.scss the following vars were injected in one of those 3 ways: $bodyFontSize, $borders, $blueColor, $grayBackgroundColor:

body {

  // Option 1) Read from webpack config
  font-size: $bodyFontSize;

  // Nesting is also possible!
  border: map_get($borders, heavy);

  // Option 2) Read from JSON or Javascript file 
  color: $blueColor; // from colors.json
  background-color: $grayBackgroundColor; // from background.js
}

with app/colors.json

{
  "blueColor": "blue",
  "redColor": "red"
}

and app/backgrounds.js

module.exports = {
  grayBackgroundColor: 'gray',
  whiteBackgroundColor: 'white',
};

Take a look at the sass-vars-loader section in webpack.config.js to see how this was done:

var path = require('path');

module.exports = {
  entry: './app/index.js',
  module: {
    rules: [{
      test: /\.scss$/,
      use: [{
        loader: "style-loader" // creates style nodes from JS strings
      }, {
        loader: "css-loader" // translates CSS into CommonJS
      }, {
        loader: "sass-loader", // compiles Sass to CSS
        options: {
          includePaths: ["app/styles.scss"],
        },
      }, {
        loader: "@epegzz/sass-vars-loader", // read Sass vars from file or options
        options: {
          // Option 1) Specify vars here
          vars: {
            bodyFontSize: '21px',

            // Nesting is also possible (use map_get to read them in scss)!
            borders: {
              heavy: '5px solid black',
              thin: '1px solid gray',
            },
          },
          // Option 2) Load vars from JSON or Javascript file
          files: [
            path.resolve(__dirname, 'app/colors.json'),
            path.resolve(__dirname, 'app/backgrounds.js'),
          ],
        },
      }],
    }],
  },
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist'),
  },
}

Usage with Extract Text Plugin

With the Extract Text Plugin the webpack.config.js changes slightly:

const path = require('path');
const ExtractTextPlugin = require('extract-text-webpack-plugin');

module.exports = {
  entry: './app/index.js',
  module: {
    rules: [{
      test: /\.scss$/,
      use: ExtractTextPlugin.extract({
        fallback: "style-loader",
        use: [{
          loader: "css-loader" // translates CSS into CommonJS
        }, {
          loader: "sass-loader", // compiles Sass to CSS
          options: {
            includePaths: ["app/styles.scss"],
          },
        }, {
          loader: "@epegzz/sass-vars-loader", // read Sass vars from file or options
          options: {
            // Option 1) Specify vars here
            vars: {
              bodyFontSize: '21px',
    
              // Nesting is also possible (use map_get to read them in scss)!
              borders: {
                heavy: '5px solid black',
                thin: '1px solid gray',
              },
            },
            // Option 2) Load vars from JSON or Javascript file
            files: [
              path.resolve(__dirname, 'app/colors.json'),
              path.resolve(__dirname, 'app/backgrounds.js'),
            ],
          },
        }],
      })
    }],
  },
  plugins: [
    new ExtractTextPlugin("styles.css"),
  ],
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist'),
  },
}

Acknowledgments

SASS var generator shamelessly copied from Kasu/jsonToSassVars.js