fix(item-set): don't leak memory when setting groups

[Thomaash]

This is my attempt at solving #183.

There are two key differences when compared to #235:

1. This one actually works better.
2. This one doesn't blindly throw away all listeners.

Leaks in my tests (very rough measurements on my device):

• Upstream: 3 MB/s
• fix: issue #183 #235: 250 KB/s
• This: about 0 KB/s

PS: For the tests I used the JSFiddle MWE from @aphix. I just decreased delays to leak more memory in shorter amount of time.

[aphix]

Great work @Thomaash! Good idea on the comments to keep people aware of some less-than-obvious interactions within the lib.

One very minor suggestion to clear up some grammar/spelling in this comment

f24b505#diff-f4d829b4f8b61a3d664fc7a5eb70924dR38-R40

I believe this:

"Anything that needs to be manually disposed off before garbage collection happens or so that garbage collection can happen should be added to this stack."

Meant to say this:

"Anything that needs to be manually disposed of before garbage collection happens (or so that garbage collection can happen) should be added to this stack."

Mostly it's the "disposed off" -> "disposed of" but I think the parenthesis help clarify the separation of the two reasons to add something to that stack.

Thanks again,
Aphix

[Thomaash]

Thanks for pointing it out. It looks better now.

[vis-bot]

🎉 This PR is included in version 7.1.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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