Functional Snake Game - Part 2 - final loop

index.js

const COLUMNS = 15
const ROWS = 15
const SPEED = 125
let uglyMutableState = initialState

const setupInput = () => {
  readline.emitKeypressEvents(process.stdin)
  process.stdin.setRawMode(true)
  process.stdin.on("keypress", (str, key) => {
    if (key.ctrl && key.name === "c") process.exit()

    const options = {
      UP: addMove(direction.NORTH),
      LEFT: addMove(direction.WEST),
      DOWN: addMove(direction.SOUTH),
      RIGHT: addMove(direction.EAST),
    }

    const move = options[key.name.toUpperCase()]
    uglyMutableState = move(uglyMutableState)
  })
}

const displayState = display(COLUMNS, ROWS)
const nextState = step(COLUMNS, ROWS)

const runGameLoop = () => {
  setInterval(() => {
    displayState(uglyMutableState)
    uglyMutableState = nextState(uglyMutableState)
  }, SPEED)
}

setupInput()
runGameLoop()