Computed (cached) function value JS pattern

cached-val-func.js

function isPrime(value) {
  // create cache
  if (!isPrime.answers) {
    isPrime.answers = {};
  }
  
  // check was value cached
  if (isPrime.answers[value] !== undefined) {
    return isPrime.answers[value];
  }
  
  var prime = value !== 0 && value !== 1; // 1 - non prime
  
  for (var i = 2; i < value; i++) {
    if (value % i === 0) {
      prime = false;
      break;
    }
  }
  
  return isPrime.answers[value] = prime;
}

console.log(isPrime(5));
console.log(isPrime(5));