Task: implement a sumSquares function that sums the squares of numbers from an array using a custom reduce function. Only the sumSquares function can be modified.

The implementation of the sumSquares function using a custom reduce function might look like this:

function sumSquares(arr) {
  return arr.reduce((acc, x) => acc + x * x, 0);
}

// Example usage:
console.log(sumSquares([1, 2, 3])); // 1 + 4 + 9 = 14

Here, reduce takes an accumulator acc and the current element x, accumulating the sum of the squares of the array elements. The initial value of the accumulator is 0.