index.js

const loaderUtils = require('loader-utils');
const SassVariablesExtract = require('./extract.js');
const camelCase = require('lodash/camelCase');
const fromPairs = require('lodash/fromPairs');

module.exports = function(content) {
  const self = this;
  const opts = loaderUtils.getOptions(self) || {};
  const callback = this.async();
  const version = this.version || 1;
  const resourcePath = this.resourcePath;
  const resolve = this.resolve.bind(this);

  this.cacheable && this.cacheable();

  const convertVariables = (variables) => {
    if (opts.preserveVariableNames) return variables;
    return variables.map(([k, v]) => [camelCase(k), v]);
  };

  try {

    SassVariablesExtract(resourcePath, resolve, content).then((result) => {
      const dependencies = result.dependencies;
      const variables = convertVariables(result.variables);
      // fromPairs will also eliminate duplicates for us
      const defaultExport = JSON.stringify(fromPairs(variables))
                       .replace(/\u2028/g, '\\u2028')
                       .replace(/\u2029/g, '\\u2029');

      // Create Module
      let module = '';
      if (version >= 2) {
        // use Map to eliminate duplicates
        new Map(variables).forEach((value, name) => {
          const constExport = JSON.stringify(value)
                           .replace(/\u2028/g, '\\u2028')
                           .replace(/\u2029/g, '\\u2029');
          module += `export var ${name} = ${constExport}\n`;
        });
        module += `export default ${defaultExport}\n`;
      } else {
        module = `module.exports = ${defaultExport}\n`;
      }

      dependencies.forEach((dependency) => {
        self.addDependency(dependency);
      });

      callback(null, module);
    }).catch((error) => {
      callback(error);
    });

  } catch (error) {
    callback(error);
  }
}