Hi, everyone,
As you know, JSON API will throw a syntax error when trying to stringify a
object with circular reference.But indeed the feature
"serializing/unserializing object with circular reference" is needed.(eg.
when storing a graph,or status machine)
I am working on a JS implement of parse/stringify to support a “path
grammar” in JSON. It looks like the following:
--------------------------------
// this will produce a object with it's property “x” reference to it self
{
x:path(/)
}
--------------------------------
//also relative path is supported
{
x:{
a:path(../x),
b:path(x)
}
}
--------------------------------
//ref to deeper object
{
x:{
a:{
obj:[]
},
b:path(/x/a/obj)
}
}
--------------------------------
// path could also point to a none-object value
{
a:11,
b:path(/a)
}
--------------------------------
// path ref to a path node will get undefined, there is no way to recurse
{
a:path(/), //the root object
b:path(/a) //undefined
}
----------------------------------
( The project is located at https://github.com/wintercn/JSONplus
. in which JSON.pareseEx and JSON.stringifyEx passes all test262 API
cases except the ones related to circular reference. )
I was wondering if the future version of ECMAScript could support this
grammar or something like this to enable serializing/unserializing object
with circular reference. It will be a good news for ones working on complex
data structure.
PS. Another known way of descripting object with circular reference is
using sharp
variable<https://developer.mozilla.org/en/Sharp_variables_in_JavaScript>
in
object literal . But there are several problems:
1. The id in sharp variable has to be unique. Combining two objects with
conflicted ids will be hard work.
2. Sharp variable is sensitive to the order of object properties. A
assignment must appear before its first usage. But path do not have such
requirement.Since the order of properties defined in JSON would
(especially) affect enumerate (for.. in) order, making a order-independent
reference grammar is a must.
3. Sharp variable requires assignment operator, and hence assignment
expression and even continuous assignment expression. Adding this feature
to JSON increases the complexity of its grammar a lot.
Thanks,
Shaofei Cheng
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