Memoization.js

function Memoization () {
 this.memo = {}
}

Memoization.prototype.fib = n => {
 // base cases
 if (n === 0 || n === 1) 
 return n

 // see if we’ve already calculated this
 if (this.memo.hasOwnProperty(n))
  console.log(`grabbing memo[ ${n} ]`)
  return this.memo[n]
 
 console.log(`computing fib( ${n} )`)
 const result = this.fib(n — 1) + this.fib(n — 2)

 // memoize
 this.memo[n] = result
 return result
}