Fibonacci sequence

Description: Write a function named fib that accepts a number n and return the number of index n

Fibonacci sequence would be something like this: [0, 1, 1, 2, 3, 5, 8, 13, 21, ...]

function fib() {

}

fib(1); // 1
fib(2); // 1
fib(8); // 21

1. Write a function to make a Fibonacci sequence

The rule is n = (n - 1) + ( n - 2)

function fib(n) {
  if (n === 0) return 0;
  if (n === 1) return 1;

  let arr = [1, 1]; // let's start from 1 not 0
  for (let i = 2; i < n; i++) {
    arr[i] = arr[i - 2] + arr[i - 1];
  }
  return arr;
}

console.log(fib(0)); // 0
console.log(fib(1)); // 1
console.log(fib(2)); // [1, 1]
console.log(fib(3)); // [1, 1, 2]
console.log(fib(4)); // [1, 1, 2, 3]
console.log(fib(5)); // [1, 1, 2, 3, 5]

2. Find the index

function fib(n) {
  if (n === 0) return 0;
  if (n === 1) return 1;

  let arr = [1, 1]; // let's start from 1 not 0
  for (let i = 2; i < n; i++) {
    arr[i] = arr[i - 2] + arr[i - 1];
  }
  return arr[n - 1];
}

console.log(fib(0)); // 0
console.log(fib(1)); // 1
console.log(fib(2)); // 1
console.log(fib(3)); // 2
console.log(fib(4)); // 3
console.log(fib(5)); // 5
console.log(fib(6)); // 8
console.log(fib(7)); // 13
console.log(fib(8)); // 21

function fib(n) {
  if (n === 0) return 0;
  if (n === 1) return 1;
  let arr = [1, 1];
  let arrIndex = 0;
  for (let i = 2; i < n; i++) {
    arr[i] = arr[i - 1] + arr[i - 2];
    arrIndex = i;
  }
  return arr[arrIndex];
}

console.log(fib(3));

Another answer:

// recursion

function fib(n) {
  if (n === 0) return 0;
  if (n === 1) return 1;
  return fib(n - 2) + fib(n - 1);
}

console.log(fib(8));

It must have end condition in recursion, in this case it's if (n === 0) return 0; and if (n === 1) return 1;