628 Maximum product of three numbers

The trick here is to take advantage of the sort method. The solution is very crafty as it takes the max from the end of the sort and multiplies it by the smallest numbers, to see that if they are negative will they produce a higher number when their sign changes. similarly, it takes the three largest numbers from the sort. The Math.max method is applied on both numbers and returns the largest.

//Given an integer array nums, find three numbers whose product is maximum and return the maximum product.

/**
 * @param {number[]} nums
 * @return {number}
 */

var maximumProduct = function (nums) {
  if (
    !Array.isArray(nums) ||
    nums.some((x) => typeof x !== 'number') ||
    nums.length < 3
  )
    return 'invalid entry';
  nums.sort((a, c) => a - c);
  return Math.max(
    nums[0] * nums[1] * nums[nums.length - 1],
    nums[nums.length - 1] *
      nums[nums.length - 2] *
      nums[nums.length - 3]
  );
};

console.log(maximumProduct([1, 2, 3]));
console.log(maximumProduct([1, 2, 3, 4]));
console.log(maximumProduct([-1, -2, -3]));
console.log(maximumProduct([-100, -98, -1, 2, 3, 4]));