Simperfy

function isIsogram(str){
    let parsedStr = '';
    str = str.toLowerCase().split('');

    for (const s of str) {
      if (parsedStr.indexOf(s) >= 0) return false;
      parsedStr += s;
    }

    return true;

Simperfy

let best = 0, sum = 0;

const arr = [1, -2, 3, -2, 3];

for (let k = 0; k < arr.length; k++) {
    sum  = Math.max(arr[k], sum+arr[k]);
    best = Math.max(best, sum);
}

console.log(best);