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# (JavaScript programming Example for Beginners)

# JavaScript Program to Check Prime Number

#### In this example, you will learn to write a JavaScript program to check if a number is a prime number or not.

A prime number is a positive integer that is only divisible by **1** and itself. For example, **2**, **3**, **5**, **7**, **11** are the first few prime numbers.

## Example: Check Prime Number

```
// program to check if a number is prime or not
// take input from the user
const number = parseInt(prompt("Enter a positive number: "));
let isPrime = true;
// check if number is equal to 1
if (number === 1) {
console.log("1 is neither prime nor composite number.");
}
// check if number is greater than 1
else if (number > 1) {
// looping through 2 to number-1
for (let i = 2; i < number; i++) {
if (number % i == 0) {
isPrime = false;
break;
}
}
if (isPrime) {
console.log(`${number} is a prime number`);
} else {
console.log(`${number} is a not prime number`);
}
}
// check if number is less than 1
else {
console.log("The number is not a prime number.");
}
```

**Output**

Enter a positive number: 23 23 is a prime number.

In the above program, the user is prompted to enter a number. The number entered by the user is checked if the number is greater than **1** using `if...else if... else`

statement.

**1**is considered neither prime nor composite.- All negative numbers are excluded because prime numbers are positive.
- Numbers greater than
**1**are tested using a`for`

loop.

The `for`

loop is used to iterate through the positive numbers to check if the number entered by the user is divisible by positive numbers(**2** to user-entered number minus **1**).

The condition `number % i == 0`

checks if the number is divisible by numbers other than 1 and itself.

- If the remainder value is evaluated to
**0**, that number is not a prime number. - The
`isPrime`variable is used to store a boolean value: either**true**or**false**. - The
`isPrime`variable is set to**false**if the number is not a prime number. - The
`isPrime`variable remains**true**if the number is a prime number.

## JS Example for Beginners: JavaScript Program to Check Prime Number

Disclaimer: The information and code presented within this recipe/tutorial is only for educational and coaching purposes for beginners and developers. Anyone can practice and apply the recipe/tutorial presented here, but the reader is taking full responsibility for his/her actions. The author (content curator) of this recipe (code / program) has made every effort to ensure the accuracy of the information was correct at time of publication. The author (content curator) does not assume and hereby disclaims any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from accident, negligence, or any other cause.The information presented here could also be found in public knowledge domains.