Is jQuery 1.4's new behavior a bad design choice?

Question

This is a bit of a rant, but also a very serous question. jQuery has changed ajax param serialization as follows:

jQuery 1.4 adds support for nested param serialization in jQuery.param, using the approach popularized by PHP, and supported by Ruby on Rails. For instance, {foo: ["bar", "baz"]} will be serialized as “foo[]=bar&foo[]=baz”.

Did you catch that?

You call your parameter foo. jQuery now renames that to foo[] behind your back if foo's value is an array. The reason for this is because some PHP-ers and Rubyists expect 3rd party APIs to rename things for them.

Call me old fashioned, but when I put something into a map, with key x, I expect to find the value under x. Or at least have this the default behavior with an optional override.

Even the documentation agrees with me:

If value is an Array, jQuery serializes multiple values with same key i.e. {foo:["bar1", "bar2"]} becomes '&foo=bar1&foo=bar2'.

Am I right in thinking this is simply a bad judgment call from the jQuery team?

Answer 1

It's actually filling in a major inconsistency, if your deserializer is aware of the convention and works with it nicely. It makes an array-of-one-thing look different from a thing-on-its-own.

Old:

• foo: "bar" maps to "foo=bar" maps to foo: "bar".
• foo: ["bar"] maps to "foo=bar" maps to foo: "bar".
• foo: ["bar", "baz"] maps to "foo=bar&foo=baz" maps to foo: ["bar", "baz"].

New:

• foo: "bar" maps to "foo=bar" maps to foo: "bar".
• foo: ["bar"] maps to "foo[]=bar" maps to foo: ["bar"].
• foo: ["bar", "baz"] maps to "foo[]=bar&foo[]=baz" maps to foo: ["bar", "baz"].

And now everything roundtrips nicely and you don't have to worry about receiving array data or non-array data depending on how many elements were in the array to begin with. For maximum elegance, foo: [] should also serialize to foo[] (a key with no value), indicating a 0-ary list, but jQuery 1.4 doesn't do that. Maybe it should. :)

Answer 2

I disagree. The old convention worked just fine, and continues to work fine for classic web workhorses like Perl's CGI.pm. I think jQuery is just switching one working convention for another, and I don't know that anybody on either side is going to be all that happy.