TypeError: Converting circular structure to JSON in nodejs

Question

I am using request package for node.js

Code :

 var formData = ({first_name:firstname,last_name:lastname,user_name:username, email:email,password:password});

  request.post({url:'http://localhost:8081/register', JSON: formData}, function(err, connection, body) {

exports.Register = function(req, res) {
    res.header("Access-Control-Allow-Origin", "*");
    console.log("Request data " +JSON.stringify(req));

Here I am getting this error :

TypeError: Converting circular structure to JSON

Can anybody tell me what is the problem

Answer 1

JSON doesn't accept circular objects - objects which reference themselves. JSON.stringify() will throw an error if it comes across one of these.

The request (req) object is circular by nature - Node does that.

In this case, because you just need to log it to the console, you can use the console's native stringifying and avoid using JSON:

console.log("Request data:");
console.log(req);

Answer 2

I also ran into this issue. It was because I forgot to await for a promise.

Answer 3

Try using this npm package. This helped me decoding the res structure from my node while using passport-azure-ad for integrating login using Microsoft account

https://www.npmjs.com/package/circular-json

You can stringify your circular structure by doing:

const str = CircularJSON.stringify(obj);

then you can convert it onto JSON using JSON parser

JSON.parse(str)

Answer 4

use this https://www.npmjs.com/package/json-stringify-safe

var stringify = require('json-stringify-safe');
var circularObj = {};
circularObj.circularRef = circularObj;
circularObj.list = [ circularObj, circularObj ];
console.log(stringify(circularObj, null, 2));


stringify(obj, serializer, indent, decycler)

Answer 5

I was able to get the values using this method, found at careerkarma.com

Output looks like this.

I just run this code in the debugger console. Pass your object to this function.
Copy paste the function also.

 const replacerFunc = () => {
    const visited = new WeakSet();
    return (key, value) => {
      if (typeof value === "object" && value !== null) {
        if (visited.has(value)) {
          return;
        }
        visited.add(value);
      }
      return value;
    };
  };
  
  JSON.stringify(circObj, replacerFunc());

Answer 6

It's because you don't an async response For example:

app.get(`${api}/users`, async (req, res) => {
    const users = await User.find()
    res.send(users);
   })

Answer 7

I forgotten to use await keyword in async function. with the given systax

blogRouter.put('/:id', async (request, response) => {
  const updatedBlog = Blog.findByIdAndUpdate(
    request.params.id,
    request.body,
    { new: true }
  );
  response.status(201).json(updatedBlog);
});

Blog.findByIdAndUpdate should be used with the await keyword.

Answer 8

This is because JavaScript structures that include circular references can't be serialized with a"plain" JSON.stringify.

https://www.npmjs.com/package/circular-json mentioned by @Dinesh is a good solution. But this npm package has been deprecated.

So use https://www.npmjs.com/package/flatted npm package directly from the creator of CircularJSON.

Simple usage. In your case, code as follows

import package

// ESM
import {parse, stringify} from 'flatted';

// CJS
const {parse, stringify} = require('flatted');

and

console.log("Request data " + stringify(req));

Answer 9

If you are sending reponse , Just use await before response

await res.json({data: req.data});

Answer 10

Came across this issue in my Node Api call when I missed to use await keyword in a async method in front of call returning Promise. I solved it by adding await keyword.

Answer 11

I came across this issue when not using async/await on a asynchronous function (api call). Hence adding them / using the promise handlers properly cleared the error.

Answer 12

I was also getting the same error, in my case it was just because of not using await with Users.findById() which returns promise, so response.status().send()/response.send() was getting called before promise is settled (fulfilled or rejected)

Code Snippet

app.get(`${ROUTES.USERS}/:id`, async (request, response) => {
    const _id = request.params.id;
    try {
        // was getting error when not used await
        const user = await User.findById(_id);
        if (!user) {
            response.status(HTTP_STATUS_CODES.NOT_FOUND).send('no user found');
        } else {
            response.send(user);
        }
    } catch (e) {
        response
            .status(HTTP_STATUS_CODES.INTERNAL_SERVER_ERROR)
            .send('Something went wrong, try again after some time.');
    }
});

Answer 13

I had a similar issue:-
const SampleFunction = async (resp,action) => {
try{
if(resp?.length > 0) {
let tempPolicy = JSON.parse(JSON.stringify(resp[0]));
do something
}
}catch(error){
console.error("consoleLogs.Utilities.XXX.YYY", error);
throw error;
}
.
.
I put await before JSON.parse(JSON.stringify(resp[0])).
This was required in my case as otherwise object was read only.
Both Object.create(resp[0]) and {...resp[0]} didn't suffice my need.

Answer 14

Try this as well

console.log(JSON.parse(JSON.stringify(req.body)));