How to check if number is prime in javascript?

Hi Friends 👋,

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To check number is a prime number, looping through 2 to your given number-1 and check is any divisible number or not, if have means it’s not a prime number.

Note: 1 is considered neither prime nor composite.

Today, I’m going to show How do I check if the number is a prime number or not in Javascript, here I will create a custom function isPrimeNumber() where I will check if there have any divisible number based on this it will return a boolean value.

Let’s start the today’s tutorial How do you check if the number is prime in JavaScript?

In the following example

1. check given value is a number
2. check given value is greater than 1
3. check given value is prime or not

Copy 
1// function to check if a number is prime or not
2function isPrimeNumber(number) {
3  // check if the passed value is a number
4  if (typeof number == 'number' && !isNaN(number)) {
5    if (number > 1) {
6      // looping through 2 to number-1
7      for (let i = 2; i < number; i++) {
8        if (number % i == 0) {
9          return false;
10          break;
11        }
12      }
13      return true;
14    }
15  }
16  return false;
17}
18
19isPrimeNumber('hello');
20isPrimeNumber(44);
21isPrimeNumber(3.4);
22isPrimeNumber(5);
23isPrimeNumber(-3.4);
24isPrimeNumber(NaN);

In the above program, we have taken examples of every possible value like parameter if string, number, positive value, a negative value, or NaN values. let’s check the output.

I hope it’s help you, All the best 👍.