Altering a JavaScript array (possibly object, too?) without replacing it doesn't appear to emit changed signals

I've witnessed this in a few different scenarios now, but only just now got around to reporting it.

When one uses JavaScript-based data, one would expect that using methods that alter that data (like push/splice/whatever on an array) would emit the changed signal - as the data has indeed changed.

It appears this isn't the case, see the attached testcase for one (really simple) example of where I've seen this happen, but I've had to work around it in a number of other areas.

(NB: I'm pretty sure this affects a lot of other versions too, this is just the one I've tested.)