Detecting and fixing circular references in JavaScript

Question

Given I have a circular reference in a large JavaScript object

And I try JSON.stringify(problematicObject)

And the browser throws

"TypeError: Converting circular structure to JSON"

(which is expected)

Then I want to find the cause of this circular reference, preferably using Chrome developer tools? Is this possible? How do you find and fix circular references in a large object?

Answer 1

Pulled from http://blog.vjeux.com/2011/javascript/cyclic-object-detection.html. One line added to detect where the cycle is. Paste this into the Chrome dev tools:

function isCyclic (obj) {
  var seenObjects = [];

  function detect (obj) {
    if (obj && typeof obj === 'object') {
      if (seenObjects.indexOf(obj) !== -1) {
        return true;
      }
      seenObjects.push(obj);
      for (var key in obj) {
        if (obj.hasOwnProperty(key) && detect(obj[key])) {
          console.log(obj, 'cycle at ' + key);
          return true;
        }
      }
    }
    return false;
  }

  return detect(obj);
}

Here's the test:

> a = {}
> b = {}
> a.b = b; b.a = a;
> isCyclic(a)
  Object {a: Object}
   "cycle at a"
  Object {b: Object}
   "cycle at b"
  true