Memoize.js

// Given a function fn, return a memoized version of that function.

// A memoized function is a function that will never be called twice with the same inputs. Instead it will return a cached value.

// You can assume there are 3 possible input functions: sum, fib, and factorial.

// sum accepts two integers a and b and returns a + b. Assume that if a value has already been cached for the arguments (b, a) where a != b, it cannot be used for the arguments (a, b). For example, if the arguments are (3, 2) and (2, 3), two separate calls should be made.
// fib accepts a single integer n and returns 1 if n <= 1 or fib(n - 1) + fib(n - 2) otherwise.
// factorial accepts a single integer n and returns 1 if n <= 1 or factorial(n - 1) * n otherwise


function memoized(fn) {
    const cachedVal = {}
    return function (...args) {
        const val = args
        if (val in cachedVal) {
            return cachedVal[val]
        }
        else {
            const result = fn(...args)
            cachedVal[val] = result
            return result
        }
    }
}