alternate_capitalization.ts

const capitalize = (s: string): [string, string] => {
    let arr01: string[] = [];
    let arr02: string[] = [];
    
    for (let i = 0; i < s.length; i++) {
        if (i % 2 === 0) {
            arr01.push(s[i].toUpperCase());
            arr02.push(s[i]);
        } else {
            arr01.push(s[i]);
            arr02.push(s[i].toUpperCase());
        }
    }
    
    return [arr01.join(""), arr02.join("")];
}

console.log(capitalize("abcdef"));      // ["AbCdEf", "aBcDeF"]
console.log(capitalize("codewars"));    // ["CoDeWaRs", "cOdEwArS"]
console.log(capitalize("codewarriors")); // ["CoDeWaRrIoRs", "cOdEwArRiOrS"]