Insertion sort

Definition

Insertion sort is a simple sorting algorithm that builds the final sorted array one element at a time. It uses comparison to find the correct position to insert the current element at, in order to maintain the sorted subarray.

Implementation

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]