Trampolined Fibonnaci

trampolined-fibonnaci.js

var trampoline = (fn) => 
 (...args) => {
    var result = fn(...args);

    while (typeof result === "function") {
      result = result()
    }

    return result
  }


var fibonnaci = trampoline((n) => {
  if (n < 2) {
    return n;
  } else {
    return () => { 
      return fibonnaci(n/*?*/ - 1) + fibonnaci(n - 2)
    }
  }
})

fibonnaci(5) //?