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I wasn't entirely sold on the splitting up of attributes and properties at first. After all, a big part of jQuery is adding convenience, and this does remove a certain amount of convenience at the end of the day, even if only a little. Then I got to the performance graphs at the end. Those are some impressive speed ups for almost all the browsers (1). The speed + more logical separation seems totally worth it.

(1) Except, you know, ie 7 and ie 8. So... half the internet.

I'd prefer the convenience, as I have yet to code up some jquery and think "damn, .attr is a dog", and now I have to refactor a bunch of code before I can upgrade, and the reality of it is that I won't. jQuery is awesome, but this is the first release that I've not wanted to jump all over

I thought about this discussion a lot more today, discussed the points with the rest of the jQuery core team, and we decided to land an improvement to bring back the boolean attribute handling (with virtually no performance overhead).

The bug and commit are as follows: http://bugs.jquery.com/ticket/9079 https://github.com/jquery/jquery/commit/a9d9f8c5422f171d9c45...

You can start using this code right now with the following version of jQuery: http://code.jquery.com/jquery-git.js

Hope this helps!

Trying to get some clarity around this commit. As I understand it this addresses usecases where an element's boolean property is set to true, and .attr() is called as a getter for said property, correct?


    .prop('selected', true)
    .attr('selected'); // undefined in 1.6, "selected" in 1.6.1

Let's pretend we're working with a checkbox that isn't checked at all:

    <input type="checkbox" id="c"/>

    $("#c").attr("checked") => false     // 1.5.2
    $("#c").attr("checked") => undefined // 1.6
    $("#c").attr("checked") => undefined // 1.6.1
The user then checks the checkbox OR we set the check by doing .prop("checked", true) OR we set the check by doing [0].checked = true, the result would be:

    $("#c").attr("checked") => true      // 1.5.2
    $("#c").attr("checked") => undefined // 1.6
    $("#c").attr("checked") => "checked" // 1.6.1
Note that if we had done .attr("checked", "checked") OR .attr("checked", true) to set the checked property then .attr("checked") would've returned "checked" in both 1.6 and 1.6.1.

In short: In jQuery 1.6.1 .attr(BooleanAttribute) now returns either the name of the attribute (if true) or undefined (if false). Which is consistent with the rest of the API and with the DOM itself.

I should note that all of this is a moot point if you're using .prop("checked") - that will just return true/false consistently based upon the current checked state of the checkbox.

Which changes (I assume, to .attr()) are affecting you, in particular?

Yes, I've since read other comments and have a better understanding of the reasoning behind .attr and .prop, so I'm a little less bah-humbug about having to refactor before upgrading. It appears that search/replace .attr('value') => .val(), .attr('checked') => .prop('checked') are the big offenders, but probably need to look closer at .attr('enabled') and .attr('disabled') as well.

Relying on the following attributes as returned from .attr() will break, and should get ported to use .prop() instead: 'checked', 'disabled', 'readonly', 'selected' (for <option>s), 'multiple' (for <select>s), 'ismap' (for <img>s), 'defer', 'noresize' (for <frame>s), 'nowrap'.

List compiled (partially) from http://stackoverflow.com/questions/706384/boolean-html-attri...

This should be linked to or listed directly in the OP.

Really, most people reading the changelog care about "how do I make my existing code work with this"--and the details listed are conceptual, but not all practically relevant.

I have this code:

  $.fn.setAttr = function(attr, bool) {
      this.attr(attr, attr);

    return this;

  $.fn.disabled = function(bool) {
    return this.setAttr('disabled', bool);

  $.fn.checked = function(bool) {
    return this.setAttr('checked', bool);
I assume I should change all attr to prop?

I think you should add two more helpers (like .val):

.checked() and .disabled() - with no parameters they return a boolean, and with a parameter you can pass in true/false to set the property.

Those two are probably the most commonly used properties and if you had them most people could probably ignore attr vs prop.

The blog entry mentions this, but perhaps without enough detail. Your `.setAttr()` exactly matches the same as the `.attr()` method's new behavior when it's passed a Boolean argument to set. The other two would be great suggestions for 1.7!

I don't think it's clear at all what the purpose of each is, especially if you were coming into jQuery fresh. I would have interpreted .prop as something more like .data.

The doc reads: "The difference between attributes and properties can be important in specific situations. Before jQuery 1.6, the .attr() method sometimes took property values into account when retrieving some attributes, which could cause inconsistent behavior. As of jQuery 1.6, the .prop() method provides a way to explicitly retrieve property values, while .attr() only retrieves attributes.

For example, consider a DOM element defined by the HTML markup <input type="checkbox" checked="checked" />..."

The docs then go into the example on this thread.

Personally, I think that if this is the only specific situation we can think of, it probably wasn't worth introducing a method that parallels attr. As a higher-level library, jQuery ideally will do the right thing without the calling code thinking too hard about exactly what mechanism it's using to do it. (It does this with cross-browser issues, for example.) This was the case already with .attr("checked")...

So if I'm approaching jQuery for the first time, do I use prop or attr, and why?

I really don't like this change. It's just confusing. Since "checked" is an attribute that has to be added to an input elemented for it to be checked, it's still an attribute.

I don't see how prop() is any different than just using data().

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