var macAddress = document.getElementById("macAddress"); function formatMAC(e) { var r = /([a-f0-9]{2})([a-f0-9]{2})/i, str = e.target.value.replace(/[^a-f0-9]/ig, ""); while (r.test(str)) { str = str.replace(r, '$1' + ':' + '$2'); } e.target.value = str.slice(0, 17); }; macAddress.addEventListener("keyup", formatMAC, false);
