Re: Improvements in Ajax facilities

> With Ajax facilities of jQuery, it is not easy to deal with errors. In
> addition, it is inconvenient to repeat reloading the same URL to
> observe changes. Please confirm my patch handles these issues.
>
> [patch for svn.208]
> http://pepper.sherry.jp/jquery/newajaxpatch-svn208.patch
>
> [test page]
> http://pepper.sherry.jp/jquery/newajaxfunc.html
>
> Problems:
> - $().load() replaces the HTML regardless of whether the request has
>   succeeded or failed. Therefore it is impossible to customize an error
>   message to show.
> - Callback functions can't learn if the request has succeeded or not.
> - It's true that there are methods that are called on error. But even
>   if it failed, DOM elements are always replaced, and callbacks are
>   always called.
> - There are no ways to set timeout. In case of a server doesn't respond,
>   we can't abort the request after a few seconds and display an error.
>
> Improvements:
> - Callbacks for $().load(), $.get, $.post now takes the second argument
>   which represents a state ("success", "failure", "notmodified").
> - $().load() no longer replaces the HTML on error, if a callback is
>   supplied. Without a callback, it replaces the HTML on error as it
>   used to do.
> - $().load(), $.get, $.post now can timeout. When it timed out, the state
>   becomes "failure" and treated as an error.
>     $.ajaxTimeout(1000); // ms
>     $().load();
> - Added 2 ajax methods:
>     $().loadIfModified();
>     $.getIfModified();
>   These methods set If-Modified-Since header to Ajax requests. They are
>   useful when we periodically reload the same URL to see changes.
>
>   They work the same way as $().load and $.get if the URL is updated.
>   When it is unchanged, ().load doesn't replace the URL but does callback.
>   In that case, the state will be "notmodified".
>
>   Since IE always returns the same cached content for the same URL, it is
>   normally impossible to check changes. It's true that it is possible to
>   force not to use cache by appending some random characters as query of
>   the URL, but then we waste the traffic needlessly. $().loadIfModified()
>   and $.getIfModified() solve this problem.
>
>
> ----
> Taku Sano
>
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