function-calcaulating.js

function buildNumber (number) {
  return (op) => {
    if (typeof op === 'function') {
      return op(number)
    }
  
    return number
  }
}

const zero = buildNumber(0)
const one = buildNumber(1)
const two = buildNumber(2)
const three = buildNumber(3)
const four = buildNumber(4)
const five = buildNumber(5)
const six = buildNumber(6)
const seven = buildNumber(7)
const eight = buildNumber(8)
const nine = buildNumber(9)

const plus = (x) => (y) => x + y
const minus = (x) => (y) => y - x
const times = (x) => (y) => x * y
const dividedBy = (x) => (y) => Math.floor(y / x)

console.assert(seven(times(five())) === 35)
console.assert(four(plus(nine())) === 13)
console.assert(eight(minus(three())) === 5)
console.assert(six(dividedBy(two())) === 3)