isPrime.js

+/**

+ * Determines if a given integer is a prime number.

+ *

+ * @param n - The number to check.

+ * @returns true if n is a prime, false otherwise.

+ */

+export function isPrime(n) {

+ // Reject non-number or non-integer inputs

+ if (typeof n !== "number" || !Number.isInteger(n)) {

+ return false;

+ }

+ // Negative numbers, 0 and 1 are not prime

+ if (n <= 1) {

+ return false;

+ }

+ // 2 and 3 are prime

+ if (n <= 3) {

+ return true;

+ }

+ // Eliminate multiples of 2 and 3 early

+ if (n % 2 === 0 || n % 3 === 0) {

+ return false;

+ }

+ // Check divisibility by numbers of the form 6k ± 1 up to sqrt(n)

+ for (let i = 5; i * i <= n; i += 6) {

+ if (n % i === 0 || n % (i + 2) === 0) {

+ return false;

+ }

+ }

+ return true;

+}