javascript add space after every 3 characters code example

Example 1: javacript string add space after commas

"1,2, 3,4,5".replace(/,(?=[^\s])/g, ", ");
> "1, 2, 3, 4, 5"

Example 2: how to put space automatically after 4 characters javascript

document.getElementById('iban').addEventListener('input', function (e) {
  e.target.value = e.target.value.replace(/[^\dA-Z]/g, '').replace(/(.{4})/g, '$1 ').trim();
});