Collatz Conjecture Function Implementation in JavaScript

collatz.js

/**
* 3x + 1 or the Collatz Conjecture is a simple mathematical conjecture
* that declares all positive integers will eventually reach a value of 1
*
* Inspiration from https://www.youtube.com/watch?v=094y1Z2wpJg
*
* @author Mark Auger
* @social Follow me on GitHub at https://github.com/swimauger
* @license
* Copyright (c) 2021 Mark Auger
* 
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* 
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
* @param {number} x `x` is **The starting number you wish to apply 3x + 1 too**
* @param {number[]} sequence `sequence` Do NOT change, sequence is used to store the sequence on each iteration
* @return {number[]}
**/
function collatz(x, sequence = [ x ]) {
  if (x % 2) {
      x = 3*x + 1;
  } else {
      x = x/2;
  }

  sequence.push(x);
  
  if (x === 1) {
      return sequence;
  } else {
      return collatz(x, sequence);
  }
}