Currying Functions with Named Parameters in JavaScript

curryNamed.js

/**
 * Currying Functions with Named Parameters.
 * @gunar, @drboolean, @dtipson 2016
 * 
 * Why does it return a thunk, though?
 *   Because in JS named arguments are opaque. There is no way of getting a function's named arguments list.
 *   e.g.
 *     const foo = function ({ a, b }) { }
 *     console.log(foo.arguments) // Throws. Ideally would return ['a', 'b'].
 * 
 * What would be an alternative?
 *   Providing a "spec". curryNamed would have to be told what the named arguments were upfront
 *   (as curryN does with numbered arguments). I personally think that's less useful.
 */
 
'use strict'

function curryNamed(fn, acc = {}) {
  return args => {
    if (!args) return fn(acc)
    return curryNamed(fn, Object.assign({}, acc, args))
  }
}

const foo = ({ a, b, c } = {}) => console.log({ a, b, c })
const bar = curryNamed(foo)

bar() // { a: undefined, b: undefined, c: undefined }

const a = bar({ a: 1 })
a() // { a: 1, b: undefined, c: undefined }

const ab = a({ b: 2 })
ab() // { a: 1, b: 2, c: undefined }

bar({ a: 1, b: 2, c: 3 })() // { a: 1, b: 2, c: 3 }

There y'all go

https://github.com/gunar/ncurry

It accepts partial application and stuff.