merge_sort.js

const merge = function(left, right, comparison) {
  const result = new Array();
  while (left.length > 0 && right.length > 0) {
    if (comparison(left[0], right[0]) <= 0) {
      result.push(left.shift());
    } else {
      result.push(right.shift());
    }
  }
  while (left.length > 0) {
    result.push(left.shift());
  }
  while (right.length > 0) {
    result.push(right.shift());
  }
  return result;
};
var merge_sort = function(array, comparison) {
  if (array.length < 2) {
    return array;
  }
  const middle = Math.ceil(array.length / 2);
  return merge(
    merge_sort(array.slice(0, middle), comparison),
    merge_sort(array.slice(middle), comparison),
    comparison
  );
};
exports.merge_sort = merge_sort;