[tomxor]

From the source the only thing I can see that would make garbage is b.innerText=o which is set 50 times each frame.

But even then it's just one giant text node, not html elements so it's surprising this is causing so much GC in Firefox.

[butz]

Looks like a job for the new profiler.firefox.com

[varenc]

Here's a profile of the freeze being caused the GC if anyone wants to try and debug: https://share.firefox.dev/487vDxG

[evilpie]

The profile actually shows the freeze is not caused by normal JS garbage collection, but by cycle collection. So probably something related to DOM nodes.