Happy Number Finder

happy_number_finder.js

(function () {

  var UNHAPPY_SEQUENCE = [4, 16, 37, 58, 89, 145, 42, 20, 4];
  var UNHAPPY_SEQUENCE_LENGTH = UNHAPPY_SEQUENCE.length;

  function calculate(number) {
    var str = '' + number;

    var length = str.length;
    var total = 0;
    var digit;

    for (var i = 0; i < length; i++) {
      digit = parseInt(str[i], 10);
      total += Math.pow(digit, 2);
    }

    return total;
  }

  function isUnhappySequence(sequence) {
    if (sequence.length < UNHAPPY_SEQUENCE_LENGTH) {
      return false;
    }

    var subSequence = sequence.slice(-9);

    if (subSequence[0] !== 4 && subSequence[8] !== 4) {
      return false;
    }

    var isUnhappy = true;

    for (var i = 0; i < UNHAPPY_SEQUENCE_LENGTH; i++) {
      isUnhappy = isUnhappy && (subSequence[i] === UNHAPPY_SEQUENCE[i]);
    }

    return isUnhappy;
  }

  function isNumberHappy(number) {
    var sequence = [];

    var isHappy = true;

    do {
      sequence.push(number);
      number = calculate(number);
      if (isUnhappySequence(sequence)) {
        isHappy = false;
        break;
      }

    } while (number !== 1);

    return isHappy;
  }

  window.isNumberHappy = isNumberHappy;
})();


var number = parseInt(process.argv[2], 10);

if (!number || number <= 0) {
  console.error('Invalid number, must be a postive integer.');
  process.exit(1);
}

var isHappy = isNumberHappy(number);

console.log('The number \"' + number + '\":');

if (isHappy) {
  console.log('Is happy! :-)');
}
else {
  console.log('Is NOT happy :-(');
}

process.exit(0);