Recursive Fibonacci in Javascript

Written by Tyler La Fronz on February 7, 2018

The Fundamentals

At its core, a basic Fibonacci algorithm is incredibly slow and inefficient. This implementation of Fibonacci includes a data structure to memorize previously calculated numbers in the sequence.

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The function that computes this

var memo = [0, 1]; //Stores the previously calculated values

function fib(fibNum) {
  var result = 0;
  if (memo[fibNum]) { //Checks for previously calculated value
    result = memo[fibNum]; //returns the value stored
  } else if (fibNum >= 2) {
    result = fib(fibNum - 1) + fib(fibNum - 2); //recursively calls for the value
    memo[fibNum] = result; //Stores the result
  return result; //returns the value