1335588 - addEventListener should not throw a TypeError if the callback is not callable

Status: RESOLVED INVALID

(Core :: DOM: Events, defect, P3)

Description

[Dennis Schubert [:denschub]]

Given the following example:

> document.addEventListener("click", 42);

In Firefox, we throw a TypeError about not being able to call "42". In Chrome, this call simply gets ignored.

Us throwing an exception is breaking some websites since it stops the JS flow. The spec clearly claims to ignore the call if the callback is null, and we should drop it if it's not callable, so we don't break stuff and to have parity with Chrome.

I've opened a spec issue at [0], and there is a WebCompat issue attached.

[0]: https://github.com/whatwg/dom/issues/405

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

We don't throw when null is passed, per DOM spec, and throw when invalid value is passed, per WebIDL spec.
Need a spec change before doing anything here, but this really sounds like a bug in Chrome.

Comment 2

[Dennis Schubert [:denschub]]

Yes, it is actually a bug in Chromium, and in fact, bz already filed it: https://bugs.chromium.org/p/chromium/issues/detail?id=676845

Closing this as invalid. Thanks!