JS Example for Beginners: JavaScript Program to Print all Prime Numbers in an Interval

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(JavaScript programming Example for Beginners)

JavaScript Program to Print all Prime Numbers in an Interval

In this example, you will learn to write a JavaScript program to print all the prime numbers between two numbers entered by a user.

A prime number is a positive integer that is only divisible by 1 and itself. For example, 235711 are the first few prime numbers.

For example, 4 is not a prime number because it is divisible by 1, 2 and 4 itself. It is a composite number.

Example: Print Prime Numbers

// program to print prime numbers between the two numbers

// take input from the user
let lowerNumber = parseInt(prompt('Enter lower number: '));
let higherNumber = parseInt(prompt('Enter higher number: '));

console.log(`The prime numbers between ${lowerNumber} and ${higherNumber} are:`);

// looping from lowerNumber to higherNumber
for (let i = lowerNumber; i <= higherNumber; i++) {
    let flag = 0;

    // looping through 2 to user input number
    for (let j = 2; j < i; j++) {
        if (i % j == 0) {
            flag = 1;

    // if number greater than 1 and not divisible by other numbers
    if (i > 1 && flag == 0) {


Enter lower number: 2
Enter higher number : 10
The prime numbers between 2 and 10 are:

In the above program, the user is prompted to enter lower and higher bound numbers. Then the prime number between those numbers(including lower and higher if any) are listed out.

Two nested for loops are used in the above program.

  • The first for loop is used to loop between the numbers provided by the user. In this case, from 2 to 10
  • A variable flag is set to 0.
  • The second for loop is used to loop between 2 to the number that is stored in i.
  • Inside the second loop, the value of i is divided by each number from 2 to value one less than i(i – 1).
  • While dividing, if any number remainder results in 0, the number is not a prime number. So the variable flag is set to 1.
  • Finally, all the numbers that have a flag 0(not divisible by other numbers) are printed.



JS Example for Beginners: JavaScript Program to Print all Prime Numbers in an Interval

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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.

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