Functional Switch in Javascript

routes.js

const callIfFunction = x => x instanceof Function ? x() : x

const choose = switchFn => // cache cases
	caseVal => callIfFunction(switchFn(caseVal)[caseVal] || switchFn().default) // get case

const agree = (x, ...list) => // agree on a fall through set
  list.find(val => x === val) || list[0] 

// make as many of these as needed
const colors = choice => ({
  ['sky']: 'blue', 
  [agree(choice, 
  'flower', 
  'lipstick', 
  'purse')]: 'purple',
  [(() => 'skittles')()]: () => 'rainbow',
  default: 'white'
})

// cache colors
const color = choose(colors)

// get color later
color('skittles') // => 'rainbow'
color('lipstick') // => 'purple'
color() // => 'white'