insertionSort javascript Code Snippet in 2025

Sorts an array of numbers, using the insertion sort algorithm.

• Use Array.prototype.reduce() to iterate over all the elements in the given array.
• If the length of the accumulator is 0, add the current element to it.
• Use Array.prototype.some() to iterate over the results in the accumulator until the correct position is found.
• Use Array.prototype.splice() to insert the current element into the accumulator.

const insertionSort = arr =>
  arr.reduce((acc, x) => {
    if (!acc.length) return [x];
    acc.some((y, j) => {
      if (x <= y) {
        acc.splice(j, 0, x);
        return true;
      }
      if (x > y && j === acc.length - 1) {
        acc.splice(j + 1, 0, x);
        return true;
      }
      return false;
    });
    return acc;
  }, []);

insertionSort([6, 3, 4, 1]); // [1, 3, 4, 6]