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from the coding point of view I'm looking for way to pass an bit array as url parameter in a small javascript application and I want to keep the parameter length as small as possible. I have an idea how to solve it, but that seems rather complicated for a problem that seems like a common one to me.

The context is the following: I'm currently trying out angularjs and wrote a simple app that is a bit like a shopping cart / configurator. I have a fairly small number of objects (>1024) and each object has a small number of configuration options (less than 6). Someone using the app might pick ~20 of these objects in a typical scenario and configure these with the tool. I'd like to make that configuration 'bookmarkable'. The App stores this configuration as an array.

I could jsonify that array I guess and pass it as url parameter, but this would be horribly long. As indicated above - all I need for each object would be 2 bytes (10 bit for the object ID and 6 bit for its configuration). Writing a function that translates my configuration array into a bit array shouldn't be difficult. If I'm not mistaken im restricted to 32 bit integers in javascript, but that shouldn't be too much trouble either. Eventually I could translate that bitarray into an integer version and use this as url parameter, but this would still a fairly long parameter and my guess is that I could make it much shorter if I'd not only use numbers in the url parameter, but as well letters.

Since this problem more or less sounds to me like a fairly common one, I'd be very happy if you could give me snippets or hints where I could look to solve the problem. If there are more effecient ways than my idea to use an array of bit arrays that's great too. I just want to avoid creating a really clumsy solution if there should be an elegant best practice version so to speak. The whole point is to get a bit more familar with javascript / angularjs.

Cheers

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How are you getting the 10 bits of the object id and the 6 configuration bits, how are they represented before "urlifying"? –  Bergi Jan 8 '14 at 13:26
    
So far it's all in json object .. something along the lines of: var myConfig = [{133,0,0,1,0,1,0},{254,0,1,1,0,1,0}],{...} .. next I'd convert those into 16 bit arrays as described here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… –  io_berlin Jan 8 '14 at 13:53
    
With the bit shift operations it should be fairly simple. –  io_berlin Jan 8 '14 at 14:00
    
That's not a valid json object, could it be an array? It would be nice if you could include the code. –  Bergi Jan 8 '14 at 14:01
    
I'll try to make a small version that I could post on fiddle - the code is pretty messy (I use it to test many different things). If it helps - the json object (array) is defined like that: `$scope.units = [ {'id': 123, 'option 1': 0, 'oprion 2' : 1}, {'id': 3, 'option 1': 1, 'option 2': 2} ]; –  io_berlin Jan 8 '14 at 14:19

3 Answers 3

up vote 0 down vote

When representing the bytes as letters, you probably will need percent encoding anyway. However, you can simply use String.fromCharCode before:

> encodeURIComponent(String.fromCharCode.apply(String, [2, 10, 20, 30, 245]))
%02%0A%14%1E%C3%B5
share|improve this answer
    
Thank you - helped me a lot. Now I know better where to look. I sometimes simply don't know the proper keywords to search for. –  io_berlin Jan 8 '14 at 14:22
up vote 0 down vote

I have a fairly small number of objects and each object has a small number of configuration options ...

For me, the model is too complicated to put all of this on URL rails.

I would create some Json object , store it into cache / localStorage with unique ID and pass in URL ID only.

On receive side, extract all stored data by ID you passed with URL.

By this way t will be easy to maintain the code and debug in case of failure.

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I see your point - I'd like to avoid any DB for this project however and see how much / what I can do with pure a javascript solution. If I should learn that attempting such is a stupid idea - better now in such test project. –  io_berlin Jan 8 '14 at 13:39
up vote 0 down vote

You can try converting your numbers to hex:

> [2,10,20,30,245].map(function(x) { return (x < 16 ? "0" : "") + x.toString(16) }).join("")
"020a141ef5"

and vice versa:

> "020a141ef5".match(/../g).map(function(x) { return parseInt(x, 16) })
[2, 10, 20, 30, 245]

This isn't the most compact coding, but the easiest one to implement.

share|improve this answer
    
Thank you for the idea - not as compact as I'd like it to be, but a nice and simple starting point. –  io_berlin Jan 8 '14 at 13:24

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