finding button used to submit a form

gistfile1.js

dojo.connect(dojo.byId("id_form"), "onsubmit", function(event) {
  dojo.query(event.target, ":active").forEach(function(node, idx, arr) {
    if (node.id == "id_button1") {
      dojo.stopEvent(event);
      // do something special of button1 is clicked
    }
  });
});