(() => {

const str = 'v13.9.0, v12.16.1, v11.15.0, v10.19.0, v9.11.2, v8.17.0, v7.10.1, v6.17.1, v5.12.0, v4.9.1';

const max_chars = 25;

let tail = max_chars;
let comma_found = null;

let lines = [];

while (tail < str.length){
    for (let i = tail; i < 0 || !comma_found; i -=1){
        if (str[i] === ','){
            comma_found = true;
            lines.push(str.slice(tail - max_chars, i + 1));
        }
    }
    comma_found = false;
    tail += max_chars;
}

const result = lines.join('\n');
console.log(result);

})();