New subject: jQuery 1.9 will remove $.browser (deprecated since jQuery 1.3 - January 2009)

7 Nov 2012

Hey all,

Just a reminder that jQuery will (after almost 4 years of deprecation!) drop
$.browser [1] in jQuery 1.9.

Please check your scripts and make sure you are are no longer using "$.browser"
(or "jQuery.browser"). After jQuery 1.9 is released, from the next MediaWiki
deployment after that $.browser will be undefined and old code trying to access
a property of it will throw a TypeError for accessing a property of undefined.

Don't be alarmed, this has been a long time coming. It's been almost 4 years,
and by the time this is deployed it will probably have been 4 years.

For those who just realised their script is still using it, or if you read this
later to fix someone else's script that just broke (hello future, did the world
end in 2012?), I'll briefly describe two migration paths you can take from
here:

== Feature detection

In most (if not all) cases of people using $.browser it is because they want
different behaviour for browsers that don't support a certain something. Please
take a minute to look at the code and find out what it is you are special-casing
for that apparently doesn't work in a certain browser.

Research on the internet and look for a way to detect this properly (examples
below). Browser detection (instead of feature detection) is not reliable, nor is
it very effective. For example, Internet Explorer has changed a lot since IE6.
Blindly doing A for IE and B for non-IE isn't very useful anymore as most (if
not all) of the new features will work fine in IE8, IE9 or IE10.

The opposite is also true. If you do something cool for Chrome, you're missing
other WebKit-based browsers that should get the same awesomeness (Safari,
Chromium, iPhone/iPod/iPad, possibly Android, Flock, etc.) these all share the
exact same engine that backs Chrome). And what if Firefox and IE also start to
support this new awesome feature?

There are many ways to do feature detection. jQuery comes with various detectors
built-in in the object "jQuery.support"[2]. This contains for example
"support.ajax",
"support.opacity" and many more[2]. You can also easily make your
own feature detector:

* var supportPlaceholder = 'placeholder ' in
document.createElement('input');
* var supportJSON = !!window.JSON;
etc.

If you need any help with feature detection, I'd recommend asking in one
of the following channels on irc.freenode.net:

* ##javascript (recommended)
* #jquery
* #wikimedia-dev

== jQuery.client [3]

If you can't figure out how to detect what you really want to switch for, there
is an elaborate plugin in MediaWiki that does the same thing that jQuery.browser
used to do (and more). This can be used as an alternative migration path. To
give an impression:

...
  jQuery.browser < {
    chrome:  true,
    version:  "22.0.1229.94",
    webkit:  true
}

...
  $.client.profile(); < {
    name:  "chrome",
    layout:  "webkit",
    layoutVersion:  537,
    platform:  "mac",
    version:  "22.0.1229.94",
    versionBase:  "22",
    versionNumber:  22
}

For example:

if ( $.browser.chrome ) {}

Would become:

++ dependency: jquery.client
var profile = $.client.profile();

if ( profile.name === 'chrome ) {}

But:

if ( $.browser.msie ) {
  // IE doesn't support opacity
  el.style.filter = 'alpha(opacity=50)';
} else { .. }

Should become:

if ( $.support.opacity ) {
  el.style.filter = 'alpha(opacity=50)';
} else { .. }

Or better yet, since this is supported by jQuery core for a while now, like
this:

 $(el).css('opacity', 0.5);

Which will do the right thing for newer browsers and old IE respectively.

-- Krinkle 

[1] http://api.jquery.com/jQuery.browser/
[2] http://api.jquery.com/jQuery.support/
[3] https://www.mediawiki.org/wiki/RL/DM#jQuery.client