a documented example of the merge function in javascript

merge.js

// 1. merge takes an already sorted left half and already sorted right half of the original array.
const merge = (left, right) => {
  let resultArr = [];
  let leftIndex = 0;
  let rightIndex = 0;

  // 2. merge crawls over these arrays creating a resulting array from the smallest values until either the left or right array is empty.
  while ((leftIndex < left.length, rightIndex < right.length)) {
    if (left[leftIndex] < right[rightIndex]) {
      resultArr.push(left[leftIndex]);
      leftIndex++;
    } else {
      resultArr.push(right[rightIndex]);
      rightIndex++;
    }
  }

 
  return resultArr
    // 3. lastly merge pushes the remaining elements of the left or right array into the result.
    .concat(left.slice(leftIndex))
    .concat(right.slice(rightIndex));
};