(() => {
let 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 lines = [];

while (str.length > 0){
    let x = str.match(/.{1,20}(?<=,)/);
    lines.push(x);
    if (!x) break;
    [ x ] = x;
    str = str.substring(x.length, str.length);
}

console.log(lines.join('\n'));

})();