default_fields.js

function genfocin(object, original) {
  return function() {
    var text = $(object).val();
    if (text == original) {
      $(object).val("");
    }
  };
}

function genfocout(object, original) {
  return function() {
    if ($(object).val() === "") {
      $(object).val(original);
    }
  };
}

$("input").focusin(
  function() {
    var text = $(this).val();
    var f = genfocin(this, text);
    $(this).focusout(genfocout(this, text));
    $(this).off("focusin");
    $(this).focusin(f);
    f();
  }
);