Kadane's Algorithm

let current_sum = 0;
let max_sum = -Infinity;

for (let i = 0; i < arr.length; i++) {
    current_sum += arr[i];
    if (current_sum > max_sum) {
        max_sum = current_sum;
    }
    if (current_sum < 0) {
        current_sum = 0;
    }
}