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Message

TypeError: cyclic object value (Firefox)
TypeError: Converting circular structure to JSON (Chrome)

Error type

TypeError

What went wrong?

When calling JSON.stringify() cyclic object reference structures can't be converted to a string.

Examples

In a circular structure like the following

var a = {};
var b = {}; 
a.child = b;
b.child = a;

JSON.stringify() will fail

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

You will need to check for cyclic object references before stringifying. For example by specifying a replacer function as the second argument of JSON.stringify().

seen = []; 

var replacer = function(key, value) {
  if (value != null && typeof value == "object") {
    if (seen.indexOf(value) >= 0) {
      return;
    }
    seen.push(value);
  }
  return value;
};

JSON.stringify(a, replacer); 
// "{"child":{}}"

Or, you can use a library or utility functions that have already been written for this scenario. For example, there is cycle.js by Douglas Crockford.

See also

  • JSON.stringify
  • cycle.js – Introduces two functions, JSON.decycle and JSON.retrocycle, which make it possible to encode cyclical structures and dags in JSON, and to then recover them.

Document Tags and Contributors

 Contributors to this page: fscholz
 Last updated by: fscholz,