All browser engines implement GC imprecisely. The JS spec permits this. In a scope with 2 inner functions (A & B) that become long-lived closures where: A captures C B captures D Both closures extend the lifetime of the *union* of the scope's captured bindings (C & D)

This conflicts with the mental model is that each closure should only retain one binding. Which leads to unintuitive memory leaks in practice.

This has been the case in engines for years. If engines could find a way to fix it, JS apps would release objects sooner & use less memory. I have wondered if a JS toolchain ("a bundler") could transparently optimize this, e.g. with a combo of function hoisting + bind()

@robpalmer2 Apache Royale does this. It works incredibly well in practice and makes arrow functions irrelevant. royale.apache.org