JS2Sass: parse JS values to Sass values

js2sass.js

const parseUnit = require('parse-unit');
const colorString = require('color-string');

// this function can receive either dart-sass or node-sass as sassEngine
module.exports = function(sassEngine) {

  return function js2sass(jsValue) {
    // UnitNumber | Color | String
    if (typeof jsValue === 'string') {
      const unitNumber = parseUnit(jsValue);
      if (!isNaN(unitNumber[0])) return new sassEngine.types.Number(...unitNumber);
      const rgbColor = colorString.get.rgb(jsValue);
      if (rgbColor != null) return new sassEngine.types.Color(...rgbColor);
      return new sassEngine.types.String(jsValue);
    } 
    // Boolean
    else if (typeof jsValue === 'boolean') {
      return jsValue
        ? sassEngine.types.Boolean.TRUE
        : sassEngine.types.Boolean.FALSE;
    } 
    // Null
    else if (typeof jsValue === 'undefined' || jsValue === null) {
      return sassEngine.types.Null.NULL;
    } else if (typeof jsValue === 'number') {
      return new sassEngine.types.Number(jsValue);
    } 
    // List -> set up and recurse
    else if (jsValue && jsValue.constructor.name === 'Array') {
      var list = new sassEngine.types.List(jsValue.length);
      for (var i = 0; i < jsValue.length; i++) {
        list.setValue(i, js2sass(jsValue[i]));
      }
      var isComma =
        typeof jsValue.separator === 'undefined' ? true : jsValue.separator;
      list.setSeparator(isComma);
      return list;
    } 
    // Map -> set up and recurse
    else if (typeof jsValue === 'object') {
      var keys = [];
      for (var k in jsValue) {
        if (jsValue.hasOwnProperty(k)) {
          keys[keys.length] = k;
        }
      }
      var map = new sassEngine.types.Map(keys.length);
      for (var m = 0; m < keys.length; m++) {
        var key = keys[m];
        map.setKey(m, new sassEngine.types.String(key));
        map.setValue(m, js2sass(jsValue[key]));
      }
      return map;
    } 
    // this shouldn't happen 😏
    else {
      throw new Error("Don't know how to coerce: " + jsValue.toString());
    }
  }
}