JavaScript: Check a number is prime or not

JavaScript Function: Exercise-8 with Solution

Write a JavaScript function that accepts a number as a parameter and checks whether it is prime or not.

Note : A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Pictorial Presentation:

Sample Solution-1:

JavaScript Code:

function test_prime(n)
{

  if (n===1)
  {
    return false;
  }
  else if(n === 2)
  {
    return true;
  }else
  {
    for(var x = 2; x < n; x++)
    {
      if(n % x === 0)
      {
        return false;
      }
    }
    return true;  
  }
}

console.log(test_prime(37));

Sample Output:

true

Flowchart:

Live Demo:

See the Pen javascript-function-exercise-8 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

Sample Solution-2:

JavaScript Code:

function test_prime(num) {
  if (num <= 1) {
    return false;
  }
  for (let i = 2; i <= Math.sqrt(num); i++) {
    if (num % i === 0) {
      return false;
    }
  }
  return true;
}
console.log(test_prime(37));
console.log(test_prime(36));

Sample Output:

true
false

Explanation:
The above function first checks if the input number is less than or equal to 1, which is not a prime number, and immediately returns false if it is. It then loops through all numbers from 2 to the square root of the input number using a for loop. It uses the modulus operator to check if each number is divisible by that number. If the input number is divisible by any number other than 1 and itself, it is not a prime number and the function returns false. Upon completion of the loop without finding a divisor, the function returns true, indicating that the input number is prime.

Flowchart:

Live Demo:

See the Pen javascript-function-exercise-8-1 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

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