315. max prime diff

main.js

let calculatedPrimes = new Set([2])

function isPrime(n) {
    let prime = true

    if (n === 1) {
        return false
    }

    if (calculatedPrimes.has(n)) {
        return true
    }

    outerLoop: for (let i=2; i <= Math.floor(n / 2); i++) {
        innerLoop: for (let j=i; j <= Math.floor(n / 2); j++) {
            let product = i * j;
            if (i * j === n) {
                prime=false
                break outerLoop
            }
            if (product > n) {
                break innerLoop
            }
        }
    }

    if (prime) {
        calculatedPrimes.add(n)
    }

    return prime
}

/**
 * @param {number[]} nums
 * @return {number}
 */
var maximumPrimeDifference = function(nums) {
    let iFirstPrime
    let iLastPrime

    for (let i=0, j=nums.length-1; iFirstPrime === undefined || iLastPrime===undefined; i++, j--) {
        if (iFirstPrime === undefined && isPrime(nums[i])) {
            iFirstPrime = i
        }

        if (iLastPrime === undefined && isPrime(nums[j])) {
            iLastPrime = j
        }
    }

    return iLastPrime - iFirstPrime
};