Error in converting circular structure to JSON in Node

[kevgeoleo]

Version

v23.6.1

Platform

Microsoft Windows NT 10.0.26100.0 x64

Subsystem

No response

What steps will reproduce the bug?

Hi,

I would like to report a bug, it can be reproduced by running the PoC below:

function test(value) {
  for (var x in this) {
  }
  JSON.stringify(this);
  var obj = {};
  Object.defineProperty(obj, "x", {
    get: function () {
      return "42";
    },
    configurable: false,
  });
  console.log(obj.x);    // 42
}
test(0);

Regards,
Kevin

How often does it reproduce? Is there a required condition?

It can be reproduced anytime by simply running the given PoC on the given Node.js version.

What is the expected behavior? Why is that the expected behavior?

Prints 42

Deno and Bun runtimes solved the problem of Converting circular structure to JSON
TypeError is only given by NodeJS

What do you see instead?

  JSON.stringify(this);
       ^

TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'global'
    --- property 'global' closes the circle
    at JSON.stringify (<anonymous>)
    at test (D:\HIWI\v8x10_05_03\reduced_20_03_2025\to_report_chunk65_round3_cluster8.js:9:8)
    at Object.<anonymous> (D:\HIWI\v8x10_05_03\reduced_20_03_2025\to_report_chunk65_round3_cluster8.js:19:1)
    at Module._compile (node:internal/modules/cjs/loader:1739:14)
    at Object..js (node:internal/modules/cjs/loader:1904:10)
    at Module.load (node:internal/modules/cjs/loader:1473:32)
    at Function._load (node:internal/modules/cjs/loader:1285:12)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:234:24)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:151:5)

Node.js v23.6.1

Additional information

No response

[ljharb]

JSON.stringify is mandated, per the JS spec, to throw on a circular reference - if it's not doing so in another runtime, please file a bug on it.

console.log doesn't necessarily have to follow these rules, ofc, but then it would be unable to use the built-in JSON tooling.

[jasnell]

This issue here really has nothing to do with JSON.stringify. It has to do with the fact that both deno and bun do not automatically capture globalThis as this in the function here.

In Node.js (and browsers), in the test(..) function in your example, this inside the function is globalThis, which has a circular reference to itself.

In both Bun and Deno, in the test(...) function, this is undefined.

Note, however, that if you change the file to be an esm in node (e.g. rename a.js to a.mjs) then this inside the function is also undefined.

Ultimately, then, this is not a bug. Things are operating as they are expected to, despite the cross-runtime inconsistency. I have verified that both Deno and Bun also throw errors on circular dependencies in JSON.stringify.

[ljharb]

(or, add "use strict"; to the top of the function scope)