Thursday, March 15th, 2007
UED - URL Encoded Data
Category: JavaScript
, Library, Remoting
UED is a tiny library that takes a hash and converts it into a URL. Instead of passing a JSON string, for example, you could just construct a URL containing the transfer object. Update: I should mention that this is more about the format than the library...UED is a proposal for a standard way to encode an object into a URL, in the same way that JSON is more a format than a library.
Since it assumes you are making GET calls, RESTful design would suggest only using UED for non-destructive calls (i.e. calls that don't change server state).
A hash is encoded like this:
JAVASCRIPT:
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//The JS Array format of the example given above
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var arr = {
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'name':"Binny",
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'year':2007,
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'quote':"Hello, World!",
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'os':['Windows','Linux','Mac'],
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'software':{
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'editor':"vi",
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'audio':"xmms",
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'video':"vlc"
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}
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}
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var data = ued_encode(arr);
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leading to a URL like this:
JAVASCRIPT:
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http://www.example.com/get_data.php?name=Binny&year=2007&
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quote=Hello%2C+World%21&os[]=Windows&os[]=Linux&os[]=Mac&
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software[editor]=vi&software[audio]=xmms&software[video]=vlc
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However, there are no server-side decoders as yet.
3.5 rating from 18 votes
That’s just a basic toQueryString-like function, right ?
Nice to have a library agnostic version around, though.
We seriously need some sort of standardization for this though, so that back-ends can pick it up more easily.
There is a limit on URL length (not sure what it is) so this technique is only good for small packets of data. Still a neat idea, especially if used in conjunction with the Image object.
Dean; it differs per browser and web server.
I can tell of at least one server-side decoder out of hand.
It’s called PHP. PHP will natively parse such data into variables and arrays. And I’m pretty sure it was written with that in mind.
I haven’t taken a close look but it appears that format is the same format both PHP and Rails uses (I believe Rails borrowed the idea from PHP).
Using xin that would be something like this:
myadress.asp?setData(’name’:”Binny”, ‘year’:2007, ‘quote’:”Hello,World!”,’os’:['Windows','Linux','Mac'],’software’:{ ‘editor’:”vi”,’audio’:”xmms”,’video’:”vlc”});
@Dean: This encoding is also useful for the post body which doesn’t have a limit and is properly encoded by PHP into the $_POST variable.
@Eric: They are similar but Rails converts objects with numeric indexes into hashes whereas PHP makes them arrays. Also, some other languages seem to not like the [] to declare arrays.. For regular hashes though they pretty much all work the same.
I recently wrote a Prototype version of this same thing that was designed primarily with PHP in mind since other languages seem to have more limited decoding schemes. It supports any combination of nested arrays and hashes when used with PHP and nested hashes at least with all other languages AFAIK. An important difference between ued_encode and mine is I use Prototype’s Hash methods rather than for.. in loops which is a necessity if you are using Prototype-extended hashes but creates a problem if you use keys named after any of prototype’s Enumerable methods (each, findAll, collect, etc..)
Test page: http://colin.mollenhour.com/posttest.php
Code: http://pastie.caboo.se/47059
Given the major differences in server-side languages’ decoding behavior I think that any complex data structures are better encoded as JSON rather than a query string.
The URL can take 2k of data… which is a pretty large sized request. But it can get even more simpler than this… just take the JSON string and escape it into the URL. Let a server side parser just get the entire querystring, decode it and parse it with a JSON library… then the rest of the processing can happen.
You end up with pretty nasty URL’s, but it handles a pretty sizable amount of data, and you can’t get any easier (no special libraries needed). The URL’s look like thus….
http://127.0.0.1:8080/something?%7BparamOne%3A%22something%22%2CparamTwo%3A%7Bid%3A12%2Cgood%3Afalse%2Cstring%3A%22something%20more%22%7D%7D
…which isn’t uber pretty, but the client and the server side are *very* happy to play with it.
This string is perfect for parse_str php function (and He calls a php page :D) but this kind of query string has different problems:
1 - it’s not standard (not implemented on every other program languages)
2 - it’s more redundant than JSON (how many times You need to write array name? arr[]= … arr[] … now think on big arrays or objects)
3 - it doesn’t preseve native variable type, in your example the year 2007 will be recieved as a string, as boolean, float, int, null and other values …
So, do we really need this “new” JSON alternative?
can anyone tell me how to get the value in the URL using javascript?
like $_GET in php and Request.QueryString in ASP.
Thanks alot.