trigger an event when someone type in a textfield

trigger an event when someone type in a textfield

hi
how can a trigger an event while someone is typing in a textfield, i tried this code:
  1. var srch = $('#txt_search');
    srch.change(function(e) {
            alert(srch.val())
    });


but i got alert when the focus come out of the textfield, what i want is everytime user press a key & textfield.value changed, event triggers.