Does setting jQuery.data() trigger an event?

Question

I'm wondering if calls to $(".domElement").data("key", "newValue") will trigger an event that I can handle? I've tried binding change but this doesn't get triggered when data is set.

I think this question may be asking something similar, but binding changeData didn't work either - jQuery data() and 'changeData' event .

Answer 1

Actually you have only tried to attach the custom event but you will also have to trigger it something like:

$('button').click(function (e) {
    $('#someID').data("key", "newValue").trigger('changeData'); 
});

$('#someID').on('changeData', function (e) {    
    alert('My Custom Event - Change Data Called! for ' + this.id);
});

FIDDLE DEMO

Answer 2

It was automatic, up until version 1.8.3 (determined by searching the source for 'changeData').

However, it's written such that 'changeData' is triggered if you do:

$element.data('key', 'newValue');

but not if you pass an object, like:

$element.data({
    'key': 'newValue'
});

Edited source excerpts to illustrate this:

jQuery.fn.extend({
    data: function( key, value ) {

        // Gets all values
        if ( key === undefined ) {
                // expurgated
            }
        // Sets multiple values
        if ( typeof key === "object" ) {
            return this.each(function() {
                jQuery.data( this, key );
            });
        }

        return jQuery.access( this, function( value ) {

            if ( value === undefined ) {
                // expurgated
            }

            parts[1] = value;
            this.each(function() {
                var self = jQuery( this );

                self.triggerHandler( "setData" + part, parts );
                jQuery.data( this, key, value );
                self.triggerHandler( "changeData" + part, parts );
            });
        },
    }
});

I'm not completely sure what jQuery.access does, but it looks to me (and testing confirmed) that the event only gets fired if you have passed the second 'newValue' argument.