Prime with Cache

gistfile1.txt

function isPrime(value) {
  if (!isPrime.answers) {
    isPrime.answers = {};
  }
  
  if (isPrime.answers[value] !== undefined) {
    return isPrime.answers[value];
  }
  
  var prime = value !== 1;
  for (var i = 2; i < value; i++) {
    if (value % i === 0) {
      prime = false;
      break;
    }
  }
  return isPrime.answers[value] = prime;
};