Денис Инешин

const prettify = (num, separator = ',') => {
  const n = num.toString();
  return n.replace(/(\d{1,3}(?=(?:\d\d\d)+(?!\d)))/g, "$1" + separator);
}

prettify(12346789); //12,346,789
prettify(12346789, '.'); //12.346.789
prettify(12346789, ' '); //12 346 789

const str = '12:30 AM';
const separate = str.replace(':', ' ').split(' '); // [12, 30, 'AM']

localStorage.setItem('foo', 'bar')
localStorage.length // 1
localStorage.foo // bar
localStorage.getItem('foo') // bar

* {
    margin: 0;
    padding: 0;
}