If you don't want to show your mask as placeholder you should use jQuery Mask Plugin.
The cleanest way:
var options = {
onKeyPress: function(phone, e, field, options) {
var masks = ['(00) 0000-00000', '(00) 00000-0000'];
var mask = (phone.length>14) ? masks[1] : masks[0];
$('.phone-input').mask(mask, options);
}
};
$('.phone-input').mask('(00) 0000-00000', options);