I have a problem JSON stringify with circular structure in javascript

Question

i try to json strigify and parse after circular structure. I want to pass to all my website my variable socket when i use socket io. In React, it's easy but the project is old and they not use React for all the project.

I use flatted library, and it's work very good for stringify but i don't get my original element. When i parse it, i get an object

const mySocket = io("monsite:1234");
const stringigy = JSON.stringify(mySocket);
localStorage.setItem("io",mySocket);

don't work because circular structure.

With Flatted

const mySocket = io("monsite:1234");
const stringigy = Flatted.stringify(mySocket);
localStorage.setItem("io",mySocket);

work but when i parse, i don't get the original value

socket = Flatted.parse(getIo);

EDIT:

Thanks for help.

It's inherently impossible to serialize a data structure that contains cycles to a format like JSON. If you flatten it, you're of course changing the structure. — Pointy
– Pointy, Commented Sep 5, 2019 at 14:52
because i want pass the socket that i create in all my website — Khol
– Khol, Commented Sep 5, 2019 at 15:24

ManUtopiK · Accepted Answer · 2019-09-05 14:58:14Z

6

A Circular structure is when a property of the object is the object itself directly (a -> a) or indirectly (a -> b -> a).

To avoid the error message, tell JSON.stringify what to do with circular reference.

The second parameter to stringify is a filter function. Here it simply converts the referred object to its ID, but you are free to do whatever you like to break the circular reference.

For example, if you have a person pointing to another person ("father"), which may (or may not) point to the original person, do the following:

JSON.stringify( that.person, function( key, value) {
  if( key == 'father') { return value.id;}
  else {return value;}
})

answered Sep 5, 2019 at 14:58

ManUtopiK

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5 Comments

Pointy Over a year ago

@Khol if you want to re-create the circular references, you'll have to come up with some annotation scheme to indicate what has to be done. It is impossible to serialize to JSON a circular structure, so any serialization inherently must change the structure.

ManUtopiK Over a year ago

If you don't know the readability of the stringified object, I suggest using CircularJSON.

ManUtopiK Over a year ago

But In fact, why do you want to stringify a socket?

Khol Over a year ago

i want to stringify it to put it in local storage like i say in my thread. I want my variable pass in all my website.

Khol Over a year ago

i use flatted, the new version of CircularJSON. i will update my thread with picture what i get when i parse after stringify

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