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How to Calculate the Least Common Multiple of Two Numbers in JavaScript


How to Calculate the Least Common Multiple of Two Numbers in JavaScript

In the realm of web development, JavaScript stands as a powerful and versatile programming language. It is widely used to create interactive and dynamic web applications. One of the essential skills for any JavaScript developer is the ability to calculate the Least Common Multiple (LCM) of two numbers programmatically. This article will serve as a comprehensive guide to help you master this skill and create JavaScript programs that can outperform others in terms of search engine rankings.

Understanding the Least Common Multiple (LCM)

Before we delve into the intricacies of JavaScript coding, it’s crucial to grasp the concept of the Least Common Multiple (LCM). The LCM of two numbers, denoted as A and B, is the smallest multiple that is divisible by both A and B. Essentially, it’s the smallest common denominator shared by two integers. To calculate this efficiently in JavaScript, we will employ an algorithm that involves finding the Greatest Common Divisor (GCD) of the two numbers.

The Algorithm to Calculate LCM

To calculate the LCM of two numbers, we will use an algorithm that consists of two main steps:

1. Find the Greatest Common Divisor (GCD)

The first step in calculating the LCM is to determine the GCD of the two numbers. The GCD is the largest number that evenly divides both A and B. We can employ the well-known Euclidean algorithm for this purpose. Here’s how it works:

  • Start with the two numbers, A and B.
  • Using a while loop, repeatedly calculate the remainder of A divided by B. Assign this remainder to B and replace A with the previous value of B.
  • Continue this process until B becomes zero. The value of A at this point will be the GCD of the original two numbers.

2. Calculate the LCM

Once we have the GCD, we can easily calculate the LCM using the following formula:

LCM(A, B) = (A * B) / GCD(A, B)

This formula leverages the relationship between the GCD and the LCM of two numbers. By dividing the product of the two numbers by their GCD, we obtain the LCM.

Writing the JavaScript Program

With a clear understanding of the algorithm, let’s proceed to write a JavaScript program that calculates the LCM of two numbers. We will encapsulate the logic in functions for reusability and clarity.

Finding the Greatest Common Divisor (GCD)

function findGCD(a, b) {
while (b !== 0) {
const temp = b;
b = a % b;
a = temp;
return a;

In this function, we use a while loop to iteratively calculate the GCD using the Euclidean algorithm. It efficiently finds the GCD of any two integers.

Calculating the LCM

function findLCM(a, b) {
return (a * b) / findGCD(a, b);

This function calculates the LCM by invoking the findGCD function we defined earlier and applying the LCM formula.

Example Usage

Let’s put our functions to the test with an example:

const num1 = 24;
const num2 = 36;
const lcm = findLCM(num1, num2);
console.log(`The LCM of ${num1} and ${num2} is ${lcm}`);

In this example, we calculate the LCM of 24 and 36, which should yield the result 72.


1. What is the practical use of finding the Least Common Multiple (LCM) in programming?

The LCM serves as a critical mathematical concept with various practical applications in programming. It is often used in scenarios such as optimizing algorithms, scheduling tasks, and solving mathematical problems that involve finding common multiples.

2. Can I use this JavaScript code for large numbers?

While the provided JavaScript code works efficiently for small to moderately large numbers, it may not be the most suitable choice for extremely large numbers. In such cases, consider implementing more advanced algorithms or using specialized libraries designed to handle large integers.

3. Are there JavaScript libraries that provide LCM functions?

Yes, the JavaScript ecosystem offers libraries like mathjs and big-integer that provide dedicated LCM functions. These libraries are well-suited for handling large numbers and offer optimized algorithms for LCM calculations.


In conclusion, we’ve embarked on a comprehensive journey to understand and implement the calculation of the Least Common Multiple (LCM) of two numbers in JavaScript. We’ve covered the fundamental concept of LCM, elucidated the algorithm, provided a step-by-step JavaScript program, and addressed common questions.

Armed with this knowledge, you now possess the skills to calculate the LCM of any two numbers efficiently using JavaScript. Remember that mastering such fundamental concepts is key to becoming a proficient JavaScript developer.

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