[OpenAjaxMobile] Dojo's (and Ext's and jQuery's) use of associative arrays as parameters

[Adam Peller]

Just a footnote to what Jon said about callbacks...  dojo.xhr uses
dojo.Deferred, which is a more generalized mechanism for callbacks, copied
from Bob Ippolito's work on Mochi kit, which in turn was inspired by
Twisted (Python).

http://mochikit.com/doc/html/MochiKit/Async.html

I don't know how consistently the associative array approach is applied in
Dojo, but I think it's generally used for one or more of the following
reasons

1) the arguments are too numerous to list out, and it would be awkward to
make some optional while they are all ordered, so the hash is a natural
solution
2) to make "future-proof" without breaking the signature
3) to allow for reuse/mixins for functions with similar args
4) because the author was object-happy

-Adam



                                                                           
             Jon                                                           
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                                       [OpenAjaxMobile] Dojo's (and Ext's  
             07/17/08 09:04 PM         and jQuery's) use of associative    
                                       arrays as parameters                
                                                                           
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I am researching the Dojo build system (which came up both in the Mobile TF
and IDE WG phone calls this week). In going through some of the Dojo
materials, I found the following example within their hello_world tutorial
at (http://dojotoolkit.org/book/dojo-book-0-9/hello-world-tutorial):

------
dojo.xhrGet({
url: 'HelloWorldResponseGET.php',
load: helloCallback,
error: helloError,
content: {name: dojo.byId('name').value }
});
------

Two things to observe: (a) the single-object associative-array approach,
(b) two callbacks (success and error).

There are other parameters to xhrGet, including timeout controls, as shown
at (http://api.dojotoolkit.org/jsdoc/dojo/HEAD/dojo.xhrGet). There are a
number of APIs in Dojo that use the single-object associative-array
approach.

I also skimmed through some of the APIs for another popular library, Ext
JS, and they also used the single-object associative-array approach in a
number of their APIs.

jQuery doesn't seem to use single-object associative-arrays as parameters
as often as Dojo and Ext JS, but it does appear in some of jQuery's APIs.

Here is what I conclude:
* JavaScript developers are able to deal with APIs that use associative
arrays to pass name-value pairs
* But none of the major toolkits goes overboard using this technique

Jon



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