TypeError: cyclic object value

TypeError: Converting circular structure to JSON (V8-based)
TypeError: cyclic object value (Firefox)
TypeError: JSON.stringify cannot serialize cyclic structures. (Safari)

The JSON format per se doesn't support object references (although an IETF draft exists), hence JSON.stringify() doesn't try to solve them and fails accordingly.

In a circular structure like the following

const circularReference = { otherData: 123 };
circularReference.myself = circularReference;

JSON.stringify() will fail

JSON.stringify(circularReference);
// TypeError: cyclic object value

To serialize circular references you can use a library that supports them (e.g. cycle.js) or implement a solution by yourself, which will require finding and replacing (or removing) the cyclic references by serializable values.

The snippet below illustrates how to find and filter (thus causing data loss) a cyclic reference by using the replacer parameter of JSON.stringify():

function getCircularReplacer() {
  const ancestors = [];
  return function (key, value) {
    if (typeof value !== "object" || value === null) {
      return value;
    }
    // `this` is the object that value is contained in,
    // i.e., its direct parent.
    while (ancestors.length > 0 && ancestors.at(-1) !== this) {
      ancestors.pop();
    }
    if (ancestors.includes(value)) {
      return "[Circular]";
    }
    ancestors.push(value);
    return value;
  };
}

JSON.stringify(circularReference, getCircularReplacer());
// {"otherData":123,"myself":"[Circular]"}

const o = {};
const notCircularReference = [o, o];
JSON.stringify(notCircularReference, getCircularReplacer());
// [{},{}]

• JSON.stringify
• cycle.js – Introduces two functions, JSON.decycle and JSON.retrocycle, which makes it possible to encode and decode cyclical structures and dags into an extended and retrocompatible JSON format.