memoize.js

/*
2623. Memoize

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.
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 memoize(fn) {
    const cache = {}

    return function(...args) {
      const key =  JSON.stringify(args)
     
      if(key in cache){
          
        return cache[key]
      }
      const output = fn(...args)
      
      cache[key] =  output
      return output
    }
}