isPrime Function - check if that num is a Prime Number or not - Javascript

Question

i want to take a value from user using prompt() and check this value if prime number or not the function must be named as isPrime and have one parameter named as num i'm already write the code but the result is => 0 isn't a prime number - 1 isn't a prime number and 3 or 4 or 5 or 6 or 7 or 8 or ..... is a prime number here i want a help to fix this mistake

let insertedValue = prompt("enter your value" , "");

for (var i = 2; i < insertedValue; i++) {
    console.log(i);
}

const isPrime =  (num) => {
    if (num == 0 || num == 1) {
        alert(`${num} isn't a prime number`);
    } else if (num / 1 == num && num / num == 1 && num % i == 0) {
        console.log(`${num} isn't a prime number`);
    } else if (num / 1 == num && num / num == 1 && num % i != 0) {
        console.log(`${num} is a prime number`);
    }
}

isPrime(insertedValue);

unclear what your problem is exactly... And insertedValue is a string, not a number. — epascarello, Jan 04 '21 at 19:19
you arent passing i to your function. if you are restricted to having just `num` as an arg then you need to loop within your funtion — Kevin Crum, Jan 04 '21 at 19:20

score -1 · Accepted Answer · answered Jan 04 '21 at 19:21

You can loop to check if the number is divisible by any integer from 2 to the square root of the number. If not, the number is prime.

let insertedValue = +prompt("enter your value" , "");
const isPrime =  (num) => {
    if(num <= 1) return false;
    for(let i = 2; i * i <= num; i++)
      if(num % i === 0) return false;
    return true;
}
alert(isPrime(insertedValue) ? `${insertedValue} is a prime number` 
     : `${insertedValue} isn't a prime number`);

isPrime Function - check if that num is a Prime Number or not - Javascript

1 Answers1