Cardcode trim input

cardcode.html

<form name="myform">
    <input type="text" name="cardcode" pattern="^([0-9]{4}\s){3}[0-9]{4}$" placeholder="×××× ×××× ×××× ××××" required>
</form>

cardCode.js

let cardInput = myform.cardcode;
cardInput.addEventListener('input', formatCardCode, false);

function formatCardCode() {
    let cardCode = this.value.replace(/[\D]/g, '').substring(0,16);
    cardCode = cardCode != '' ? cardCode.match(/.{1,4}/g).join(' ') : '';
    this.value = cardCode;
}