# JavaScript: Greatest common divisor (gcd) of two integers

## JavaScript Math: Exercise-8 with Solution

Write a JavaScript function to get the greatest common divisor (GCD) of two integers.

**Note:**

According to Wikipedia - In mathematics, the greatest common divisor (gcd) of two or more integers, when at least one of them is not zero, is the largest positive integer that divides the numbers without a remainder. For example, the GCD of 8 and 12 is 4.

*Test Data* :

console.log(gcd_two_numbers(12, 13));

console.log(gcd_two_numbers(9, 3));

*Output *:

1

3

**Visual Presentation:**

**Sample Solution-1:**

**JavaScript Code:**

```
// Define a function named gcd_two_numbers that calculates the greatest common divisor (GCD) of two numbers.
function gcd_two_numbers(x, y) {
// Check if both x and y are of type number, if not, return false.
if ((typeof x !== 'number') || (typeof y !== 'number'))
return false;
// Take the absolute values of x and y to ensure positivity.
x = Math.abs(x);
y = Math.abs(y);
// Iterate using the Euclidean algorithm to find the GCD.
while(y) {
// Store the value of y in a temporary variable t.
var t = y;
// Calculate the remainder of x divided by y and assign it to y.
y = x % y;
// Assign the value of t (previous value of y) to x.
x = t;
}
// Return the GCD, which is stored in x after the loop.
return x;
}
// Output the GCD of 12 and 13 to the console.
console.log(gcd_two_numbers(12, 13));
// Output the GCD of 9 and 3 to the console.
console.log(gcd_two_numbers(9, 3));
```

Output:

1 3

**Flowchart:**

**Sample Solution-2:**

Calculates the greatest common divisor between two or more numbers/arrays.

- The inner _gcd function uses recursion.
- Base case is when y equals 0. In this case, return x.
- Otherwise, return the GCD of y and the remainder of the division x/y.

**JavaScript Code:**

```
// Source: https://bit.ly/3hEZdCl
// Define a constant named gcd which calculates the greatest common divisor (GCD) of multiple numbers.
const gcd = (...arr) => {
// Define an inner function _gcd to calculate the GCD of two numbers using the Euclidean algorithm.
const _gcd = (x, y) => (!y ? x : gcd(y, x % y));
// Reduce the array of numbers to find the GCD of all numbers.
return [...arr].reduce((a, b) => _gcd(a, b));
};
// Output the GCD of 12 and 13 to the console.
console.log(gcd(12, 13));
// Output the GCD of 9 and 3 to the console.
console.log(gcd(9, 3));
// Output the GCD of 8 and 36 to the console.
console.log(gcd(8, 36));
// Output the GCD of 12, 8, and 32 using the spread operator to pass the array elements individually.
console.log(gcd(...[12, 8, 32]));
```

Output:

1 3 4 4

**Flowchart:**

**Live Demo: **

See the Pen javascript-math-exercise-8 by w3resource (@w3resource) on CodePen.

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