Binding multiple events of the same type?

Question

Firstly, is it possible? Been struggling with this one for hours; I think the reason my events aren't firing is because one event is unbinding/overwriting the other. I want to bind two change events to the same element. How can I do that?

---

As per request, here's the function I'm struggling with:

(function($) {
    $.fn.cascade = function(name, trigger, url) {
    var cache = {};
    var queue = {};

        this.each(function() {
            var $input = $(this);
            var $trigger = $input.closest('tr').prev('tr').find(trigger);

            //$input.hide();

            var addOptions = function($select, options) {
                $select.append('<option value="">- Select -</option>');
                for(var i in options) {
                    $select.append('<option value="{0}">{1}</option>'.format(options[i][0], options[i][1]));
                }
                $select.val($input.val()).trigger('change');
            }

            var $select = $('<select>')
                // copy classes
                .attr('class', $input.attr('class'))
                // update hidden input
                .bind('change', function() {
                    $input.val($(this).val());
                })
                // save data for chaining
                .data('name', name)
                .data('trigger', $trigger);

            $input.after($select);

            $trigger.bind('change', function() {
                var value = $(this).val();

                $select.empty();

                if(value == '' || value == null) {
                    $select.trigger('change');
                    return;
                }

                // TODO: cache should be a jagged multi-dimensional array for nested triggers
                if(value in cache) {
                    addOptions($select, cache[value]);
                } else if(value in queue) {
                    $select.addClass('loading');
                    queue[value].push($select);
                } else {
                    var getDict = {}
                    getDict[name] = value;
                    // TODO: use recursion to chain up more than one level of triggers
                    if($(this).data('trigger')) {
                        getDict[$(this).data('name')] = $(this).data('trigger').val();
                    }
                    $select.addClass('loading');
                    queue[value] = [$select];
                    $.getJSON(url, getDict, function(options) {
                        cache[value] = options;
                        while(queue[value].length > 0) {
                            var $select = queue[value].pop();
                            $select.removeClass('loading');
                            addOptions($select, options);
                        }
                    });
                }
            }).trigger('change');
        });

        return this;
    }
})(jQuery);

The relevant chunk of HTML is even longer... but essentially it's a select box with a bunch of years, and then an <input> that gets (visibly) replaced with a <select> showing the vehicle makes for that year, and then another <input> that gets replaced with the models for that make/year.

Actually, it seems to be running pretty well now except for on page load. The initial values are getting wiped.

---

Solved the issue by pulling out that $select.bind() bit and making it live:

$('select.province').live('change', function() { 
    $(this).siblings('input.province').val($(this).val()); 
});
$('select.make').live('change', function() { 
    $(this).siblings('input.make').val($(this).val()); 
});
$('select.model').live('change', function() { 
    $(this).siblings('input.model').val($(this).val()); 
});

Sucks that it's hard-coded in there for my individual cases though. Ideally, I'd like to encapsulate all the logic in that function. So that I can just have

$('input.province').cascade('country', 'select.country', '/get-provinces.json');
$('input.make').cascade('year', 'select.year', '/get-makes.json');
$('input.model').cascade('make', 'select.make', '/get-models.json');

Answer 1

I am actually not sure exactly if you can bind two different change events. But, why not use logic to complete both events? For example...

$('input:checkbox').change(function() {
  // Do thing #1.
  // Do thing #2.
});

That way, you get the same benefit. Now, if there are two different things you need to do, you may need to use logic so that only one or the other thing happens, but I think you would have to do that anyway, even if you can bind two change events to the same element.

Answer 2

Yes that is possible.

$(…).change(function () { /* fn1 */ })
    .change(function () { /* fn2 */ });

jQuery event binding is additive, calling .change a second time does not remove the original event handler.

Answer 3

Ryan is correct in jQuery being additive, although if you find there are problems because you are chaining the same event, beautiful jQuery allows another approach, and that is calling the second function within the first after completion of the first as shown below.

$('input:checkbox').change(function() {
  // Do thing #1.;  <-- don't forget your semi-colon here
  (function() {
     // Do thing #2.
  });

});

I use this technique frequently with form validation, one function for checking and replacing disallowed characters input, and the second for running a regex on the results of the parent function.

Update to Post:

OK... You all are quick to beat on me with your negative scores, without understanding the difference in how we each view Mark's request. I will proceed to explain by example why my approach is the better one, as it allows for the greatest flexibility and control. I have thrown up a quick example at the link below. A picture's worth a 1000 words.

Nested Functions on One Event Trigger

This example shows how you can tie in three functions to just one change event, and also how the second and third functions can be controlled independently, even though they are still triggered by the parent change event. This also shows how programmatically the second and third functions can BOTH be tied into the same parent function trigger, yet respond either with or independently (see this by UNCHECKING the checkbox) of the parent function it is nested within.

$('#thecheckbox').change(function() { 

      $("#doOne").fadeIn();

      if ($('#thecheckbox').attr('checked')) { doFunc2() }
      else { doFunc3() };

      function doFunc2() { $("#doTwo").fadeIn(); return true; }
      function doFunc3() { $("#doTwo").fadeOut(); return true; }

      $("#doThree").fadeIn();

  });

I've included the third 'Do thing #3 in the example, to show how yet another event can follow the two nested functions as described earlier.

Forgive the earlier bad pseudocode originally posted first, as I always use ID's with my jQuery because of their ability to give everything an individual status to address with jQuery. I never use the 'input:checkbox' method in my own coding, as this relies on the 'type' attribute of an input statement, and therefore would require extra processing to isolate any desired checkbox if there is more than one checkbox in the document. Hopefully, the example will succeed at articulating what my comments here have not.