TypeError: cyclic object value

The JavaScript exception "cyclic object value" occurs when object references were found in JSON. JSON.stringify() doesn't try to solve them and fails accordingly.

Message

TypeError: cyclic object value (Firefox)
TypeError: Converting circular structure to JSON (Chrome and Opera)
TypeError: Circular reference in value argument not supported (Edge)

Error type

TypeError

What went wrong?

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.

Examples

Circular references

In a circular structure like the following

var 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():

const getCircularReplacer = () => {
  const seen = new WeakSet();
  return (key, value) => {
    if (typeof value === "object" && value !== null) {
      if (seen.has(value)) {
        return;
      }
      seen.add(value);
    }
    return value;
  };
};

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

See also

• 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.