.clone() documentation is incorrect

[ithcy]

As noted in this stackoverflow question:

The API for clone() says:

The .clone() method performs a deep copy of the set of matched
elements, meaning that it copies the matched elements as well as all
of their descendant elements and text nodes. For performance reasons,
the dynamic state of form elements (e.g., user data typed into input, and textarea or user selections made to a select) is not copied
to the cloned elements. The clone operation sets these fields to
their default values as specified in the HTML.

The docs appear to be wrong. User data typed into inputs is indeed copied to the cloned elements. I verified this with several tests. I could not get .clone() to not copy the value of a text input that whose value was empty in the HTML. The value of the cloned element must be explicitly cleared after cloning if this is the desired result.

[dmethvin]

If this is now happening I am thinking it might be because the browsers changed their behavior. Do you have a test case showing the behavior for all inputs including things like textarea as well? Does it happen consistently in all browsers?

[ithcy]

Here's a test case: http://jsbin.com/OKExOvu/1/edit?html,js,output

It only happens with text inputs and checkboxes. Textareas and selects do not retain user input/selection. So my pull request should probably change to reflect that.

It happens in Chrome, Firefox and IE as far back as IE8 (IE7 not tested). So it's not a browser change.
It happens with all versions of jQuery from 2.x-git all the way back through 1.2.3. (via google CDN). So it's not a new jQuery behavior.

Since this appears to be so embedded, I'm thinking it's probably better to change the documentation than try to patch jQuery, since there may be applications depending on this behavior.

There are also several other questions on stackoverflow referencing this issue. The answers all recommend clearing the value of the new element after cloning.

[dmethvin]

Thanks for doing the legwork on this @ithcy. I did seem to remember that textarea didn't retain its data on a clone. The only place where we special-case inside jQuery is with check boxes, where the behavior wasn't consistent across browsers.

If you could update the pull request to mention the exceptions you found, that would be great!

[ithcy]

No problem! Test case updated to include checkboxes, which do appear to retain their [un]checked state when cloned. I will update the pull request shortly.