How to Find Prime Numbers in an Array in Javascript

In this tutorial, you will learn how to find prime numbers in an array in javascript. The number which is divisible only by itself and 1 is known as a prime number. For example 2, 3, 5, 7, etc.  An array is a collection of items and those items can be of similar or different types.

In this case, we are only going to have numbers in the array. There are numerous ways to find prime numbers in an array. Since we are dealing with arrays, we have access to various methods and properties related to arrays.  One of those methods is the filter() method which will be enough to get the job done.

In the following example, we have an array of numbers and upon click of a button, we will find prime numbers and display them on the screen.  Please have a look over the code example and the steps given below.


  • We have 3 elements in the HTML file (div, button, and h1). The div element is just a wrapper for the rest of the elements.
  • The innerText for the button element is “Get” and for the h1 element, it is “Result”.
  • We have done some basic styling using CSS and added the link to our style.css stylesheet inside the head element.
  • We have also included our javascript file script.js with a script tag at the bottom.
<!DOCTYPE html>
<html lang="en">

  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link rel="stylesheet" href="style.css">


  <div class="container">    

  <script src="script.js"></script>

.container {        
    text-align: center;

button {
  margin-top: 10px;
  padding: 10px 20px;


  • We have selected the button element and h1 element using the document.querySelector() method and stored them in btnGet and output variables respectively.
  • We have global array numbers which contains some random numbers.
  • We have attached a click event listener to the button element.
  • In the event handler function, we are using the filter() method to get only prime numbers from the array. As you already know, the filter() method returns an array and we are storing that in the primeNumbers variable.
  • We have the isPrime() method which will take a number as a parameter. It will verify whether the number is prime or not and will return a Boolean value.
  • We are converting the primeNumbers array into the string using the toString() method and storing that in the result variable.
  • We are displaying the result in the h1 element using the innerText property.
let btnGet = document.querySelector("button");
let output = document.querySelector("h1");

let numbers = [22, 11, 51, 7, 8, 19, 28, 36];

btnGet.addEventListener("click", () => {
  let primeNumbers = numbers.filter((num) => isPrime(num));
  let result = primeNumbers.toString();
  output.innerText = result;

function isPrime(num) {
  for (let i = 2; i < num; i++) {
    if (num % i === 0) return false;
  return num > 1;