Attempting to `console.log()` `DOMException.prototype` throws error

[samualtnorman]

Version

v20.19.5, v22.19.0, v24.8.0

Platform

Linux samual-nixos 6.12.48 #1-NixOS SMP PREEMPT_DYNAMIC Fri Sep 19 14:35:52 UTC 2025 x86_64 GNU/Linux

Subsystem

Console

What steps will reproduce the bug?

Evaluate console.log(DOMException.prototype) in any way.

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

Every time.

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

Simply print the object to the terminal. That's what browsers do.

What do you see instead?

Welcome to Node.js v24.8.0.
Type ".help" for more information.
> console.log(DOMException.prototype)
Uncaught TypeError: Value of "this" must be of DOMException
    at throwInvalidThisError (node:internal/per_context/domexception:29:15)
    at get name (node:internal/per_context/domexception:133:7)
    at formatError (node:internal/util/inspect:1633:20)
    at formatRaw (node:internal/util/inspect:1067:14)
    at formatValue (node:internal/util/inspect:922:10)
    at inspect (node:internal/util/inspect:409:10)
    at formatWithOptionsInternal (node:internal/util/inspect:2574:40)
    at formatWithOptions (node:internal/util/inspect:2436:10)
    at console.value (node:internal/console/constructor:336:14) {
  code: 'ERR_INVALID_THIS'
}

Additional information

No response

[ljharb]

In a browser, that logs undefined, and it's a data property.

In node, Object.getOwnPropertyDescriptor(DOMException, 'prototype') also fails, and that should not even be possible.

[samualtnorman]

In a browser, that logs undefined, and it's a data property.

In node, Object.getOwnPropertyDescriptor(DOMException, 'prototype') also fails, and that should not even be possible.

how are you getting it to log undefined?
here's firefox:

here's chrome:

In Node.js, I assume you're trying to run it in the REPL and the REPL is trying to print the object to the terminal using the same thing console.log() uses (I assume it's using util.inspect() or whatever util.inspect() is an abstraction for).

Try > void Object.getOwnPropertyDescriptor(DOMException, 'prototype').

[ljharb]

You're right, it's the inspection that's causing the problem, and it's failing on the first key name.

I now see that if i do DOMException.prototype.name or DOMException.prototype directly in the repl, it fails, and in Safari, it just logs undefined (i guess safari's console log implementation logs undefined when it throws). Chrome does something weird and different.

What does the HTML spec say about this?

[Fayti1703]

What does the HTML spec say about this?

WebIDL says that invoking a getter on an object that doesn't implement the appropriate interface throws a TypeError. (The case of accessing it on the prototype object is directly called out elsewhere -- note that DOMException::name is not annotated with LegacyLenientThis). So that part seems correct.

The Console standard is... frustratingly silent on error handling: it says nothing about how to handle errors during printing or formatting. (Which can occur if you try to %s format an object like { toString() { throw new Error("nope") } } -- from a quick test: Firefox seems to silently discard the entire console.log() call in this case, Chrome propagates the exception).

[ljharb]

In that case, it seems like node's well within its rights to do whatever it wants here, so while node may choose to do something different, it's not a bug as-is?

[samualtnorman]

Node.js console.log() implementation could throw for every every object passed in if it wanted, that doesn't make it good or useful behaviour.
It's not a bug in the context of the spec but I don't think the spec is a good context for deciding what's a bug in this case. I think it's a bug in the context of Node.js.