JS Curried Function (Converter)

curried-function-converter.js

const converterOld = (toUnit, factor, offset, input) => {
  const converterOffset = offset || 0;
  return [((converterOffset + input) * factor).toFixed(2), toUnit].join(' ');
};

const convert10MilesToKm = converterOld('km', 1.60936, undefined, 10);
const convert20MilesToKm = converterOld('km', 1.60936, undefined, 20);
const convert30MilesToKm = converterOld('km', 1.60936, undefined, 30);

console.log('convert10MilesToKm : ', convert10MilesToKm); //  "16.09 km"
console.log('convert20MilesToKm : ', convert20MilesToKm); //  "32.19 km"
console.log('convert30MilesToKm : ', convert30MilesToKm); //  "48.28 km"