Insertion Sort implemented in JavaScript

insertion_sort.js

/* This method works by building up a sorted array at the beginning of 
 * the list. It begins the sorted array with the first element. Then it 
 * inspects the next element and swaps it backwards into the sorted 
 * array until it is in sorted position. It continues iterating through 
 * the list and swapping new items backwards into the sorted portion 
 * until it reaches the end.
 */
'use strict';

// insert - puts a number in the right spot in an array in ascending order
// Parameters are the number to add and the ordered array
const insert = (n, arr) => {
  // Make a clean copy of the array
  const copy = [...arr];

  // Loop through
  for (let i = 0; i < copy.length; i++) {
    // Put n into the array before the first entry that is 
    // greater than or equal to it
    if (n <= copy[i]) {
      copy.splice(i, 0, n);
      return copy;
    }
    // If the function hasn't returned by the end of the loop, 
    // n is greater than the others and goes at the end
    if (i === copy.length - 1) {
      copy.splice(i + 1, 0, n);
      return copy;
    }
  }
  // Fallback
  return copy;
};

// Tests
console.log(insert(3, [1, 2, 4])); // [1, 2, 3, 4]
console.log(insert(5, [1, 2, 4])); // [1, 2, 4, 5]
console.log(insert(2, [1, 2, 4])); // [1, 2, 2, 4]

// insertionSort - implement insertion sort
// uses the insert function
const insertionSort = array => {
  // clean copy
  const copy = [...array];
  // an array that starts with a single item
  let sorted = [array[0]];
  // loop through the copy, ignoring the item already in sorted
  for (let i = 1; i < copy.length; i++) {
    // insert each copy item into the sorted array, in order,
    // using the insert function
    sorted = insert(copy[i], sorted);
  }
  // return sorted array
  return sorted;
};

// Tests
console.log(insertionSort([1, 4, 2, 8, 345, 123, 43, 32, 5643, 63, 123, 43, 2, 55, 1, 234, 92])); 
// [1, 1, 2, 2, 4, 8, 32, 43, 55, 63, 92, 123, 123, 234, 345, 5643]