simulate lift using js

lift-kata.js

const initialState = {
  floor: 0,
  isOpen: false,
  direction: 'up',
}

function Lift (state = initialState) {
  console.table(state)

  function request (floor) {
    return Lift({
      ...state,
      direction,
      floor
    })
  }

  function setFloor(floor) {
    return Lift({
      ...state,
      floor
    })
  }

  function open () {
    return Lift({
      ...state,
      isOpen: true
    })
  }

  function close () {
    return Lift({
      ...state,
      isOpen: false
    })
  }

  return {
    open,
    close,
    request
  }
}

function LiftQueue (lift) {
  return function (liftTarget, callback) {

    if (lift.floor !== liftTarget.floor) {
      setTimeout(() => {
        console.log("DING!")
        liftTarget.open().close()
        callback(LiftQueue(liftTarget))
      }, Math.abs(lift.floor - liftTarget.floor) * 1000)
    }
  }
}

running:
copy this script to some REPL like in the browser

  Lift()
    .setFloor(4), 
  function(callToLiftAgain) { 
    // you can call the lift once at time the lift has arrived 
    callToLiftAgain( Lift().setFloor(1) )
  }
)```