Functional Utils

ifElse.js

const ifElse = (condition, whenTrue, whenFalse) => {
  return (...args) => 
    condition(...args) 
    ? whenTrue(...args) 
    : whenFalse(...args)
}

const identity = x => () => x
const inc = x => x + 1

const incIfInt = ifElse(Number.isInteger, inc, identity(NaN))
incIfInt('1') // NaN
incIfInt(1) // 2

sequence-compose.js

// [Ramda pipe](http://ramdajs.com/docs/#pipe)
const sequence = (...operations) => {
  const apply = (result, operation, index) => 
    index !== 0
    ? operation(result) 
    : operation(...result)
  return (...o) => operations.reduce(apply, o)
}

const negate = x => -x
const inc = x => x + 1
sequence(Math.pow, negate, inc)(3, 4) // -(3^4) + 1

// [Ramda compose](http://ramdajs.com/docs/#compose)
const compose = (...operations) => sequence(...operations.reverse())

const sum = x => y => x + y
const multiply = (x, y) => x * y
compose(Math.abs, sum(1), multiply)(2, -4) // 7