builderWithoutClass.js

const flightBuilder = () => {
  let flight = {}
  
  const builder = {
    withFlightCode: (flightCode) => {
      flight.flightCode = flightCode
      return builder
    },

    withStops: (stops) => {
      flight.stops = stops
      return builder
    },

    build: () => {
      return flight
    }
  }

  return builder
}

console.log(flightBuilder().withFlightCode('XL1234').withStops(2).build())