jsonpickleJS

Javascript reinterpretation of Python jsonpickle to allow reading and (to a lesser extent)
writing JSON objects

Pre-class-based system (Closing down)

Note for 2025+: This system depends on legacy style functions that behave like objects.
To use with modern Javascript you will need to assign all classes to globalThis (window, global).
For this reason, v1.2 will be the last version of jsonpickleJS. Using custom decoders in JSON.parse
is probably the best solution going forward in the modern world.

Python to Javascript and Back

Python has a remarkable number of ways (for a language that believes there's only one way to do it)
to transfer data between itself and Javascript, most obviously with the
`json.dump()/json.dumps()

 calls, which work well on specifically created data, especially
of primitive objects. It also has a good number of ways to store the contents of an object so that
it could be reloaded later into the same Python interpreter/session. The most well known of these
is the

pickle module, which stores the Python data as binary data.

The external jsonpicklemodule, which you'll need to have installed to make this module have any sense, combines the features ofjson and pickle, storing Python data in a JSON (Javascript Object Notation) string, viajsonpickle.encode()that can be parsed back byjsonpickle.decode()to get nearly all data types restored to their previous state. (Highly recommended: jsonpickle v1.7 or higher. Older versions will not serialize recursive data structures as necessary for a lot of applications.)

Since JSON is one of the most easily parsed formats in Javascript (the name should be a giveaway), this project, jsonpickleJS, exists to parse the output of Python's jsonpickle into objects in Javascript. The constructors of the objects need to have the same names and exist in the global namespace, such aswindow, in the Javascript. For instance, if you have a class calledmyobject.Thingin Python, you'll need to have a Prototype constructor function calledwindow.myobject.Thingin Javascript. The object, and any subobjects, will be created as closely as possible in Javascript.

The reverse is also possible, with some caveats. Since Javascript didn't (until ECMAScript 6) have the concept of named classes, each object needed to have a marker somewhere on it saying what Python object it should convert back to. The marker iso[jsonpickle.tags.PY_CLASS] = 'fully.qualified.ClassName'. It may be possible in the future to useinstanceofthrough the entire Global namespace to figure out what something is, but that seems rather dangerous and inefficient (A project for later).

`Limitations`


Remember that Javascript does not have tuples, so all tuple objects are changed to lists.
Namedtuples behave the same way, I believe. Dicts and Objects are identical in Javascript (both
a blessing and a curse).
Security

Pickle, jsonpickle, and jsonpickleJS all raise important security considerations you must be
aware of. You will be loading data directly into Python or Javascript with no checks on what the
data contains. Only load data you have personally produced if you want to be safe.  In Javascript,
malicious data may compromise your browser, browser history, functioning of the current web page,
etc. That's pretty bad, but nothing compared to what can happen if you load jsonpickle data
from Javascript into Python: a maliciously written set of jsonpickle data may be able to send the
contents of any file back to the net or manipulate or delete the hard drive of the server. It may
be that the parsed Python object have to be called in some way, but it may even be possible to have
malicious code executed just on parsing; assume the worst. Your .html/.js may only produce safe
data, but anyone with JS programming experience can inject other data into your server scripts. 
Be safe: be cautious going from Python to Javascript and NEVER accept Javascript-produced
jsonpickle data from the net into your Python program in any sort of open environment.
Usage

You can use jsonpickleJSin modern JavaScript environments with either ES Modules or traditional

`

This works without any build system. The jsonpickle global will be available automatically.

`$3`

You can find a working example in testUnpickle.html.

`$3`

jsonpickleJSallows you to decode Python-style JSON strings into rich JavaScript objects. It’s especially useful for projects that mirror data structures across Python and JavaScript.

One real-world use case: Older versions ofmusic21andmusic21j use jsonpickleJSto render complex musical objects in the browser — such as using.show('vexflow')in music21 to visualize music sent from Python into JavaScript.

`Building`


Run once:


% npm install


Then:

`% npm run build``

jsonpickleJS

Javascript reinterpretation of Python jsonpickle to allow reading and (to a lesser extent)
writing JSON objects

Pre-class-based system (Closing down)

Python to Javascript and Back

Python has a remarkable number of ways (for a language that believes there's only one way to do it)
to transfer data between itself and Javascript, most obviously with the
`json.dump()/json.dumps()

 calls, which work well on specifically created data, especially
of primitive objects. It also has a good number of ways to store the contents of an object so that
it could be reloaded later into the same Python interpreter/session. The most well known of these
is the

pickle module, which stores the Python data as binary data.

`Limitations`


Remember that Javascript does not have tuples, so all tuple objects are changed to lists.
Namedtuples behave the same way, I believe. Dicts and Objects are identical in Javascript (both
a blessing and a curse).
Security

Pickle, jsonpickle, and jsonpickleJS all raise important security considerations you must be
aware of. You will be loading data directly into Python or Javascript with no checks on what the
data contains. Only load data you have personally produced if you want to be safe.  In Javascript,
malicious data may compromise your browser, browser history, functioning of the current web page,
etc. That's pretty bad, but nothing compared to what can happen if you load jsonpickle data
from Javascript into Python: a maliciously written set of jsonpickle data may be able to send the
contents of any file back to the net or manipulate or delete the hard drive of the server. It may
be that the parsed Python object have to be called in some way, but it may even be possible to have
malicious code executed just on parsing; assume the worst. Your .html/.js may only produce safe
data, but anyone with JS programming experience can inject other data into your server scripts. 
Be safe: be cautious going from Python to Javascript and NEVER accept Javascript-produced
jsonpickle data from the net into your Python program in any sort of open environment.
Usage

You can use jsonpickleJSin modern JavaScript environments with either ES Modules or traditional

`

This works without any build system. The jsonpickle global will be available automatically.

`$3`

You can find a working example in testUnpickle.html.

`$3`

jsonpickleJSallows you to decode Python-style JSON strings into rich JavaScript objects. It’s especially useful for projects that mirror data structures across Python and JavaScript.

`Building`


Run once:


% npm install


Then:

`% npm run build``