Why does he need to manually do the tracing or reference counting of all these nodes?
Instead, he could just use the references he needs in the new tree, delete/override the old tree's root node, and expect the Javascript GC to discard all the nodes that are now referenced.
> Then, my plan was to construct a ProseMirror transaction that would turn the old tree into the new one. To do that, it’s helpful to know which nodes appeared in the old document, but not the new one.
So, it's not actually about reclaiming the memory. It's about taking some action on the nodes that will be reclaimed. It's akin to a destructor/finalizer, but I need that to happen synchronously at a time that I control. JavaScript does now support finalization (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...) but it can't be relied on to actually happen, which makes it useless in this scenario.
Instead, he could just use the references he needs in the new tree, delete/override the old tree's root node, and expect the Javascript GC to discard all the nodes that are now referenced.