How to use Recursion In Javascript

The recursion method to print the whole Fibonacci series till a certain number is not recommended because, recursion algorithm itself is costly in terms of time and complexity, and along with fetching a Fibonacci series number at a certain position, we need to store them in an array, which calls the recursive function again and again for each and every element, i.e, n times!

The recursion method can be applied as follows in JavaScript.

Javascript
function fibonacci(n) {

    // Return value for n = 1
    if (n == 1) return 0;

    // Return value for n = 2
    if (n == 2) return 1;

    // Recursive call
    return fibonacci(n - 1) + fibonacci(n - 2);
}

const n = 10;

// Create a new array of size 'n'
let series = new Array(n);

// Fills all places in array with 0
series.fill(0);

for (let i = 1; i <= n; i++) {

    // Store i-th Fibonacci number
    series[i - 1] = fibonacci(i);
}

// Print the series
console.log(series);

Output
[
  0, 1,  1,  2,  3,
  5, 8, 13, 21, 34
]




How to calculate the Fibonacci series in JavaScript ?

Fibonacci series is a number series that contains integers in the following pattern.

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, ..

In terms of mathematics, the general formula for calculating the Fibonacci series is

fn = fn-1 + fn-2 , where n ≥ 2

Here, f0 = 0 and f1 = 1.

We need to calculate n Fibonacci numbers for any given integer n, where n ≥ 0.

Example:

Input   : n = 5
Output : [0, 1, 1, 2, 3]
Input : n = 10
Output : [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

In this article, we are focusing on two major and common ways for calculating the Fibonacci series.

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