y combinator + currying with ES7 (JavaScript)

let yCombinator = f => (g => (...p) => f(g(g))(...p))(g => (...p) => f(g(g))(...p))

var factory = f => (...a) => a.length - a[0].length > 1 ? f.call.call(...a) : f.bind(null, ...a)
//
//    we could add some fancy code to eliminate fn.call & fn.bind		
//			
//    var topsy = (f => f.bind(f))(Function.call)		
//    var turvy = (f => f.bind(f))(Function.bind)
//    var factory = f => (...a) => (a.length - a[0].length > 1 ? topsy : turvy(f, null))(...a)
//
//    in fact, we could eliminate .call in the expression altogether
//    var factory = ((f => g => (...a) => (a.length - a[0].length > 1 ? f : f.bind(f, f.bind, g, g.bind))(...a)()())((f => f(f.bind))(f => f.bind(f)))


let bind = yCombinator(factory)


// demo case 1: currying
let log = (a, b) => console.log(a, b)
bind(log)(null, 2, 5)
bind(log)(null)(2, 5)
bind(log)(null, 2)(5)
bind(log)(null)(2)(5)
bind(log, null, 2, 5)
bind(log, null)(2, 5)


// demo case 2: recursion
let fib = f => n => n < 3 ? 1 : ( f(n - 1) + f(n - 2) )

console.log(
  yCombinator(fib)(10)
)

console.log(
  yCombinator(fib)(10)
)

// demo case3: recursion and currying
let metaFib = (f, n) => n < 3 ? 1 : ( f(n - 1) + f(n - 2) )

// bind(metaFib, null) add padding context `null` to metaFib and create a high order function like `fib`
console.log(
  yCombinator(bind(metaFib, null))(10)
)

console.log(
  yCombinator(bind(metaFib)(null))(10)
)