https://www.reddit.com/r/dailyprogrammer/comments/36cyxf/20150518_challenge_215_easy_sad_cycles/

sad-cycle.js

if (process.argv.length !== 4) {
  console.log("Usage:", process.argv[1], "b start")
  return;
}

var b = parseInt(process.argv[2]),
  start = parseInt(process.argv[3]);

if (isNaN(b) || isNaN(start)) {
  console.log("need numbers");
  return;
}

var mathIt = function (exp, num) {
  var ind = (num + "").split(""),
    total = 0;
  for (var i = 0; i < ind.length; ++i) {
    total += Math.pow(ind[i], exp);
  }
  return total;
};

var findPattern = function (numbers) {
  if (numbers.length <= 1) {
    return;
  }

  var newNumber = numbers.slice(-1)[0];
  var idx = numbers.slice(0, -1).indexOf(newNumber)
  if (idx !== -1) {
    return numbers.slice(idx, -1);
  }
  return null;
}

var sadCycle = function (exp, num) {
  var results = [],
    pattern = null;

  while (!pattern) {
    num = mathIt(exp, num);
    results.push(num);
    pattern = findPattern(results);
  }

  return pattern;
}

console.log(sadCycle(b, start));