javascript fibonacci series

function fibonacci(n) {
   return n < 1 ? 0
        : n <= 2 ? 1
        : fibonacci(n - 1) + fibonacci(n - 2);
}

console.log(fibonacci(4));

// number fibonnaci to array format
function fibonacci(nums) {
  
  let fib = [0, 1];
  let data = [];
  
  for(let i = 2; i <= nums; i++) {
    fib[i] = fib[i - 1] + fib[i - 2]; 
    data.push(fib[i]);
  }
  
  return data;
}

const fibo = (n, memo = {}) => memo[n] || (n <= 2 ? 1 : (memo[n] = fibo(n - 1, memo) + fibo(n - 2, memo)));

// Examples
fibo(6);    // 8