/**
* @function fibonacci
* @description Fibonacci is the sum of previous two fibonacci numbers.
* @param {Integer} N - The input integer
* @return {Integer} fibonacci of N.
* @see [Fibonacci_Numbers](https://en.wikipedia.org/wiki/Fibonacci_number)
*/
const fibonacci = (N) => {
if (!Number.isInteger(N)) {
throw new TypeError('Input should be integer')
}
// memoize the last two numbers
let firstNumber = 0
let secondNumber = 1
for (let i = 1; i < N; i++) {
const sumOfNumbers = firstNumber + secondNumber
// update last two numbers
firstNumber = secondNumber
secondNumber = sumOfNumbers
}
return N ? secondNumber : firstNumber
}
export { fibonacci }