Memoized fib

fib.js

function fib(n) {
    var res = {}
    function step(t) {
        if (res[t]) {
            return res[t]
        }

        if (t <= 1) {
            res[t] = t
        } else {
            res[t] = step(t-1) + step(t-2)
        }
        return res[t]
    }
  return step(n)
}

function naiveFib(n) {
    if (n <= 1) {
        return n
    } else {
        return naiveFib(n-1) + naiveFib(n-2)
    }
}

var t0 = performance.now()
console.log(fib(30))
var t1 = performance.now()
console.log(`took ${t1-t0}ms`)

t0 = performance.now()
console.log(naiveFib(30))
t1 = performance.now()
console.log(`took ${t1-t0}ms`)