JS Phone Number Formatter

js

/*** PHONE NUMBER FORMATTER ***/
    function phoneFormat(input) {
        // Strip all characters except digits
        input = input.replace(/\D/g, '');
        // Trim input to ten characters, to preserve phone format
        input = input.substring(0, 10);
        // Format string based on length
        var size = input.length;
        if (size == 0) {
            input = input;
        } else if (size < 3) {
            input = '(' + input;
        } else if (size < 6) {
            input = '(' + input.substring(0, 3) + ') ' + input.substring(3, 6);
        } else {
            input = '(' + input.substring(0, 3) + ') ' + input.substring(3, 6) + '-' + input.substring(6, 10);
        }
        return input;
    }
    // KEY BINDING
    document.getElementById('eventContactPhone').addEventListener('keyup', function(evt) {
        var phoneNumber = document.getElementById('eventContactPhone');
        var charCode = (evt.which) ? evt.which : evt.keyCode;
        phoneNumber.value = phoneFormat(phoneNumber.value);
    });
    //Before Submit document.getElementById('eventContactPhone').value.replace(/\D/g,'');
    /*** PHONE NUMBER FORMATTER ***/