Collatz Conjecture - Javascript

collatz.js

// Standalone Collatz Conjecture function (https://en.wikipedia.org/wiki/Collatz_conjecture)
const collatz = (input) => {
  let result = [];
  let value = input;
  
  while(value != 1) {
    value = (value % 2 === 0) ? value / 2 : value * 3 + 1;

    result.push(value)
  }
  
  return result;
};

// Returns some information about the number that generates the bigger sequence of integers
const collatzAnalysis = function(input) {
    if(!input || isNaN(input)) {
      throw new Error('Input parameter must be a number');
    }

    console.time('Time spent to calculate Collatz');

    // Variables declarations
    var value = 0,
        number = input,
        biggestSequence,
        items = {},
        totalItems = 0;
    
    // Iterates over the input value example: if input = 1000, goes from 1000, 998, 997 ... until 2
    while(input != 1) {
      value = input;
      biggestSequence = 0;

      while(value != 1) {
        value = (value % 2 === 0) ? value / 2 : value * 3 + 1;
        
        const index = input.toString();
        if(!items[index]) {
          items[index] = [];
        }
        
        items[index].push(value);
        biggestSequence++;
      }
      // Checks if the there is a bigger sequence than the stored previously
      if(biggestSequence > totalItems) {
        totalItems = biggestSequence;
        number = input;
      }
      input--;
    }
    items = items[number.toString];
    console.timeEnd('Time spent to calculate Collatz');
    console.log(`Number ${number} produces the bigger sequence containing ${totalItems} items.`);

    return {
      number,     // the number that returns the bigger sequence of numbers
      items,      // the greater sequence of numbers 
      totalItems  // the size of the greater sequence of numbers
    }
  }