Parse variables in a SASS file into an ES module

sass-variable-parser.js

const fs = require("fs");
const byline = require("byline");
const camelCase = require('lodash.camelcase')

const inputFile = "./colors.scss";
const outputFile = "./colors.js";

const sassVarDeclaration = /^\$(.*)\:\s(\S*)(?:\s\!default\;|\;)$/;
const isReference = val => val.startsWith("$");
const getReferenceName = val => val.slice(1);

async function main() {
  // Read SCSS file line-by-line
  const stream = byline(fs.createReadStream(inputFile, { encoding: "utf8" }));

  // Process SCSS lines
  const vars = new Map();

  stream.on("data", line => {
    const matched = line.match(sassVarDeclaration);
    if (!matched) return;
    const name = matched[1];
    const value = matched[2];
    if (isReference(value)) {
      const referencedValue = vars.get(getReferenceName(value));
      if (!referencedValue) {
        throw Error(`Referenced SCSS variable '${value}' is not defined`);
      }
      vars.set(name, value);
    } else {
      vars.set(name, value);
    }
  });

  // Write JS file
  stream.on("finish", () => {
    let outString = "";
    vars.forEach((v, k) => {
      const safeVariableName = camelCase(k)
      outString = outString.concat(`export const ${safeVariableName} = "${v}"; // ${k}\n`)
    });

    fs.writeFile(outputFile, outString, () => console.log(outString));
  });
}

main();

Example:

In:

// colors.scss
$blue = #00f;
$primary-color = $blue;

Out:

// colors.js
export const blue = "#00f"; // blue
export const primaryColor = "#00f"; // primary-color