How to Pass Custom Parameters to Event Handler

Question

Just getting started with Dojo. I want to pass a couple of custom parameters to an event handler. In jQuery, you can do it like this:

$('#button').click({
    customData: 'foo'
}, handlerFunction);

And customData can be accessed from handlerFunction like this:

function handlerFunction(event) {
    console.log(event.data.customData);
}

I'm migrating a bit of jQuery code over to Dojo. How can I pass those parameters to the Dojo event handler?

Answer 1

Well, generaly, closures allow you to pass "hidden" parameters to a function:

function make_event_handler(customData){
    return function(evt){
        //customData can be used here
        //just like any other normal variable
        console.log(customData);
    }
}

So when connecting an event in dojo:

dojo.connect(node, 'onclick', make_event_handler(17));

Another possibility that I like a lot is using dojo.partial / dojo.hitch to create the closures for you.

function event_handler(customData, evt){
     ///
}

dojo.connect(node, 'onclick', dojo.partial(event_handler, 17))

---

Note that all of these these required your event handlers to be created with passing the extra parameter(s) in mind. I don't know if you can do a more direct translation of the JQuery code since that would require extra massaging of the evt variable and I don't think dojo does that.