The main problem with the JavaScript GCD algorithm is that it can take a long time to calculate.

function gcd(a, b) { if (b == 0) { return a; } else { return gcd(b, a % b); } }

This is a recursive function to calculate the greatest common divisor of two numbers, using Euclid’s algorithm.

If b is equal to 0, then the GCD is equal to a. Otherwise, the GCD is equal to the GCD of b and the remainder of a divided by b.

## Greatest Common Dividor

The Greatest Common Divisor (GCD) of two integers is the largest integer that divides both integers without leaving a remainder. For example, the GCD of 12 and 24 is 6.

## Math libraries

There are a few libraries that can help with math in JavaScript. One is Math.js, which provides a number of basic math functions and objects. Another is numeral.js, which provides a comprehensive set of numeric functions and objects.

## Recursion in JavaScript

Recursion is a programming construct that allows a function to call itself. In other words, it allows a function to refer to itself in its own definition. Recursion can be used to solve problems or achieve certain goals.

One common use of recursion is in algorithms that solve problems using loops. For example, the Fibonacci sequence can be solved using a recursive algorithm. The algorithm starts by calculating the Fibonacci number for the first time, and then calculating the Fibonacci number for the second time based on the result of the first calculation. This process is repeated until either the sequence reaches a predetermined limit or until an error occurs.

Recursive functions can also be used to solve problems involving lists and arrays. For example, suppose you want to find all of the even numbers between 2 and 100. You could use a loop to do this, but it would take quite a bit of time to run. Instead, you could use recursion to calculate all of the even numbers between 2 and 100 using a single function call.