io.js

/**
 * Usage:
 * function fn([{a, b}, out], c) {
 *   out.c = c
 *   out.d = a + b + c
 * }
 * 
 * const obj = {a: 1, b: 2}
 * io(fn, obj, 3)
 * console.log(obj) // obj = {a: 1, b: 2, c: 3, d: 6}
 */

export default function io (fn, input, ...args) {
  return fn.call(this, [input, input], ...args)
}