fib.js

function fib(n){
    const result = [0,1]
    for(let i = 2; i <= n; i ++){
      const a = result[i - 1];
      const b = result[i -2 ];
      
      result.push(a +b)
    }
    return result[n]
  }
  
  fib(6)
  
  function fib(n){
    if (n < 2){
      return n;
    }
    return fib(n-1) + fib(n-2)
  }
  
  function memoize(fn){
    const cache = {};
    return function(...args){
      if (cache[args]){
        return cache[args];
      }
      const result = fn.apply(this,args);
      cache[args] = result;
      return result;
    }
  }
  fib = memoize(fib);
  fib(100)

//O(n) no memo
  const fibonacciRecursive = (n) => {
    const result = [0,1];
    let count = 2;
    const recurse = (n) => {
      if (count <= n){
        const a = result[count-1];
        const b = result[count-2];
        result.push(a+b);
        count++;
        recurse(n);
      }
    };
    recurse(n);
    return result[n];
  };
  fibonacciRecursive(6);