Insertion sort is ES6

insertionSort.js

/**
 * Insertion sort
 * @param {array} arr - Array of numbers
 */
const insertionSort = (arr = []) => {
  const length = arr.length;

  for (let i = 1; i < length; i++) {
    const item = arr[i];
    let j = i - 1;

    while (j >= 0 && arr[j] > item) {
      arr[j + 1] = arr[j];
      arr[j] = item;
      j--;
    }
  }
};