Find the maximum subarray of a JavaScript array

Finding the maximum contiguous subarray within an array of numbers is a common problem in computer science. It's often used to solve coding challenges and interview questions. The problem can be solved using a greedy approach that keeps track of the current sum and the maximum sum found so far.

Define variables to keep track of the maximum start index, sMax, maximum end index, eMax and current start index, s. Starting with a maxSum of -Infinity and a sum of 0, use Array.prototype.forEach() to iterate over the array and add elements to the sum.

If the sum becomes negative, reset it to 0 and update the value of s to the next index. If the sum is greater than the maximum sum found so far, update the maximum sum and the start and end indices of the subarray. Finally, return the subarray using Array.prototype.slice().

const maxSubarray = (...arr) => {
  let maxSum = -Infinity, sum = 0;
  let sMax = 0, eMax = arr.length - 1, s = 0;

  arr.forEach((n, i) => {
    sum += n;
    if (maxSum < sum) {
      maxSum = sum;
      sMax = s;
      eMax = i;
    }

    if (sum < 0) {
      sum = 0;
      s = i + 1;
    }
  });

  return arr.slice(sMax, eMax + 1);
};


maxSubarray(-2, 1, -3, 4, -1, 2, 1, -5, 4); // [4, -1, 2, 1]