sass-var-to-css-var.js

import { promises as fs } from 'fs';
const targets = [
  '/path/to/anything.scss',
];
const noticeComment = '// Generated CSS variables from Scss Variables';

await Promise.all(
  targets.map(async (target) => {
    const scss = await fs.readFile(target, 'utf-8');
    const indexOfNoticeComment = scss.indexOf(noticeComment);
    const cleanedupScss =
      indexOfNoticeComment > -1
        ? scss.substring(0, indexOfNoticeComment)
        : scss;
    const vars = [...cleanedupScss.matchAll(/\$(.+?)\s*:\s*.+;/g)];
    const cssVariables = vars
      .map(([, name]) => {
        return `--${name}: #{$${name}};`;
      })
      .join('\n  ');

    await fs.writeFile(
      target,
      `${cleanedupScss.replace(
        /\n*$/,
        ''
      )}${'\n'}${'\n'}${noticeComment}${'\n'}:root {${'\n  '}${cssVariables}${'\n'}}${'\n'}`
    );
  })
);