primes.ts

const assert = require("assert");

const nextPrime = (primes: Array<number>) : number => {
  if(primes.length == 0)
  {
    return 2;
  }else if(primes.length == 1)
  {
    return 3;
  }
  
  let i = primes[primes.length-1] + 2;
  while(!primes.every(p => i % p !== 0))
  {  
    i = i + 2;
  }
  return i;
}

assert.equal(nextPrime([2]), 3);
assert.equal(nextPrime([2,3]), 5);
assert.equal(nextPrime([2,3,5]), 7);

const isPrime = (n: number) : boolean => {

  if(n < 2)
  {
    return false; 
  }

  let halfN = Math.round(n / 2) +1;
  
  let i = 2; 
  let primes = [];
  while(i< halfN)
  {
    if(n % i === 0)
    {
      return false; 
    }
    primes.push(i);
    i = nextPrime(primes);
    //nextPrime( currentPrimes)
  }

  return true; 
}

const scenarios : Array<[number, boolean]> = [
  [0, false],
  [1, false],
  [2, true],
  [3, true],
  [4, false],
  [13, true],
  [294979, true],
  [5445067, true], //timeout
  [95328227, true],
  [2756621611, true],
]

scenarios.forEach(([n, expected]) =>{
  console.log(`isPrime:${n} expected:${expected}`);
  assert.equal(isPrime(n), expected);
});

console.log('done');