//HTML BUTTON
<button type="button" onclick="disableAll()">Disable</button>
//Jquery function
function disableAll() {
//DISABLE ALL FIELDS THAT ARE NOT DISABLED
$('form').find(':input:not(:disabled)').prop('disabled', true);
//ENABLE ALL FIELDS THAT DISABLED
//$('form').find(':input(:disabled)').prop('disabled', false);
}