$.data don't behave the same as $.fn.data with data-* attributes

[Pomeh <pomeh13@…>]

The bug is about jQuery.data and jQuery.fn.data.

Tests

I ran tests with jQuery version 1.4.4, on Windows Vista (please don't blame me!) and on following browsers:

• Internet Explorer Beta 9.0.7960 (with all document modes 9, 8 and 7)
• Chrome 8.0.552
• Firefox 3.6.13

I ran the same tests, except for IE 9, on Windows XP. All tests confirm the unexpected behavior.

I've create a test case here: ​http://jsfiddle.net/pomeh/bJ6Nh/

Description

If we have a DOM element "myDomElement" which has a "data-state" attribute and its value "my-state-value", a call to jQuery.data(myDomElement, 'state') returns "undefined" instead of "my-state-value".

But a call to jQuery(myDomElement).data('state') returns the right value ("my-state-value").

Also, as shown in the test case, if we first call to jQuery(myDomElement).data('state') and then we try jQuery.data(myDomElement, 'state'), this time the value will be correct.

Correction

I think the reason of the bug is simple:

• first, jQuery.data doesn't get data-* values because the call to internal "dataAttr" method occurs only in the jQuery.fn.data method (see ​https://github.com/jquery/jquery/blob/master/src/data.js#L158)
• second, why two successive calls to jQuery.fn.data and jQuery.data fixes the issue is because the internal "dataAttr" method store the value with a call to jQuery.data (see ​https://github.com/jquery/jquery/blob/master/src/data.js#L224)

[dmethvin]

It's intentional that jQuery.data does not pull data- attributes; only the jQuery.fn.data method does that. Was there some documentation you saw that indicated otherwise?

[Pomeh <pomeh13@…>]

Replying to dmethvin:

It's intentional that jQuery.data does not pull data- attributes; only the jQuery.fn.data method does that. Was there some documentation you saw that indicated otherwise?

No there wasn't, but I was expected they works the same way, that's ok maybe I'm wrong I'm sorry.

But if they don't and won't works the same way, there's still a problem. Looks at this: ​http://jsbin.com/ahicu4/edit (sorry about JS Bin but jsFiddle is down right now). The problem is that when you call first $.fn.data *then* $.data on the same element, the $.data return the data-* attributes !

That's because $.fn.data pull those attributes and store them into the internal cache, then $.data read that cache, so the value is retrieved.

So the way you call $.data may alter the value being retrieved.

[john]

Yeah, this is the intended behavior. As a end-user you should be interacting directly with jQuery.fn.data.