Experiment: render Bootstrap variables to JSON file

jsonify-bootstrap.js

let fs = require('fs');
let path = require('path');
let less = require('less');
let bluebird = require('bluebird');
let css = require('css');

async function execute() {
  let variablesLess = await bluebird.fromNode(cb => fs.readFile(path.join(__dirname, 'less/variables.less'), 'utf-8', cb));
  let [parseResult] = await bluebird.fromNode(cb => less.parse(variablesLess, cb));
  let varNames = parseResult.rules
    .map(r => r.name)
    .filter(r => r);

  let hackLess = varNames
    .map(n => `.${n.slice(1)} { background-color: ${n}; }`)
    .join('\n');
  hackLess = '@import "less/variables";\n' + hackLess;

  let hackCss = (await less.render(hackLess)).css;
  await bluebird.fromNode(cb => fs.writeFile('testoutput.css', hackCss, cb));
  let cssAst = css.parse(hackCss);

  let jsVars = cssAst.stylesheet.rules.map(rule => {
    let varName = rule.selectors[0].slice(1);
    let jsName = [...varName].reduce((obj, nextChar) => {
      if (nextChar === '-') {
        obj.nextIsCap = true;
        return obj;
      }
      if (obj.nextIsCap) {
        obj.nextIsCap = false;
        nextChar = nextChar.toUpperCase();
      }
      obj.name += nextChar;
      return obj;
    }, {
      nextIsCap: false,
      name: ''
    }).name;
    let value = rule.declarations[0].value;
    return {key: jsName, value};
  });

  let jsonVars = jsVars.reduce((obj, next) => {
    obj[next.key] = next.value;
    return obj;
  }, {});

  await bluebird.fromNode(cb => fs.writeFile('variables.json', JSON.stringify(jsonVars, null, 2), cb));
}

execute()
  .catch(err => {
    console.error(err);
    process.exit(1);
  });