inputName.value = inputName.defaultValue
if(inputName.value == '')
but jQuery doesn't have a built-in method for retrieving that default value. Thankfully, google found me a super easy workaround - this discussion thread holds the key:
var defVal = $(this).defaultValue;
if ($(this).val() == "")
Note the  in the defaultValue. As explained in the thread linked above: "If you imagine $(this) as an array of DOM objects within jQuery, then $(this) is a way to access the first (or in this case, only) DOM object. jQuery doesn't have a built in way to retrieve the default value of an input, so we have to nip back into the DOM momentarily in order to retrieve it. "