#10027 closed bug (wontfix)
jQuery.hasData returns false for elements with HTML5 data- attributes in the markup
Reported by: | Owned by: | Rick Waldron | |
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Priority: | blocker | Milestone: | |
Component: | data | Version: | 1.6.1 |
Keywords: | Cc: | ||
Blocked by: | Blocking: |
Description
<table> <tr> <td id="test" data-priority="1">Description of status</td> </tr> </table>
$.hasData(document.getElementById('test')); // returns false $('#test').data(); // returns Object { priority: 1 }
If HTML5 data attributes are recognised by the data() method then $.hasData() should also recognise them.
Change History (10)
comment:1 Changed 12 years ago by
comment:2 Changed 12 years ago by
Component: | unfiled → data |
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Owner: | set to Rick Waldron |
Priority: | undecided → blocker |
Status: | new → assigned |
comment:3 Changed 12 years ago by
Milestone: | None → 1.6.3 |
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comment:5 Changed 12 years ago by
We are unfortunately overloading a lot of meanings onto the word "data" here based on different standards and conventions. Originally it was just the "data" representing jQuery's data-binding feature but we have asymmetrically extended it to include the "data" representing the data-
attributes on an element.
The reason .hasData()
exists is to provide a way for jQuery internals to determine if a jQuery data object (i.e., an entry in jQuery.cache
) exists for a DOM element *without actually creating one*. That cannot be done with jQuery.data()
because that method is documented to return a newly created and attached data object if none previously existed.
For performance reasons, we only grab the data-
attributes once, the first time that jQuery.fn.data
is called to read an attribute that is not defined, or when it is first called to read the entire data object (see #8909). (Note that jQuery.data
doesn't pull in data-
attributes, but *will* read the cached values once they are cached.) If you ask for data-
attributes after that, you're using cached values and not the actual attribute values off the markup.
If you need to answer the question "Tell me if any data-
attributes are on this element at all -- I haven't got any idea of their possible names", and you want to know the *current* state as opposed to the jQuery-cached-data state of those values, you'll need to do what jQuery.fn.data
does -- enumerate *all* attributes, looking for ones starting data-
. That could be expensive.
Can anyone come up with a common need for something like this? Since the internal jQuery.cache
entry that jQuery.data()
reads won't necessarily match up with the real-time data-
attributes I think it might do more harm than good to provide it.
And yes, I think we've made a mess of this.
comment:6 Changed 12 years ago by
Blocking: | 10026 added |
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comment:7 Changed 11 years ago by
Resolution: | → wontfix |
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Status: | assigned → closed |
If you need to find out whether there are any data-
attributes, use $().data()
and a for/in loop to examine the result. The required semantics of .hasData()
do not allow it to go looking for data-
attributes.
comment:8 Changed 11 years ago by
If you need a "hasData" solution, the following will sufficiently meet that need:
http://jsfiddle.net/rwaldron/Um8MF/
(function( $ ) { $.fn.hasData = function() { var data = jQuery(this).data(); for ( var prop in data ) { return true; } return false; }; })( jQuery ); console.log( $("#a").hasData(), $("#b").hasData() );
comment:9 Changed 11 years ago by
Milestone: | 1.6.3 |
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comment:10 Changed 11 years ago by
Blocking: | 10026 removed |
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(In #10026) We will not be directly writing to data-* attrs with the jQuery data api
As requested, here is a jsFiddle demonstrating above: http://jsfiddle.net/sNKrd/1/
(view with eg Firebug console enabled)