Finding the nth prime number in JavaScript

We are required to write a JavaScript function that takes in a number as the only argument, let's call the number n. The function should find and return the nth prime number from the starting.

For example −

if n = 6, then the output should be: 13

Example

Following is the code −

const findPrime = num => {
   let i, primes = [2, 3], n = 5;
   const isPrime = n => {
      let i = 1, p = primes[i],
      limit = Math.ceil(Math.sqrt(n));
      while (p <= limit) {
         if (n % p === 0) {
            return false;
         }
         i += 1;
         p = primes[i];
      }
      return true;
   }
   for (i = 2; i <= num; i += 1) {
      while (!isPrime(n)) {
         n += 2;
      }
      primes.push(n);
      n += 2;
   };
   return primes[num - 1];
}
console.log(findPrime(6));
console.log(findPrime(16));
console.log(findPrime(66));

Output

Following is the output on console −

13
53
317

AmitDiwan

Published on 10-Dec-2020 07:49:32

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