Why does var not help garbage collection in blocks in JavaScript?
Because var is function-scoped, not block-scoped. A var inside a block leaks to the enclosing function scope and stays alive until the function returns, even if the block has ended. let and const are freed when the block ends.
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More FAQs in Garbage Collection and Block Scope in JavaScript
When a block ends, its lexical environment is eligible for GC (unless a closure keeps it alive). This lets the GC free block-scoped variables sooner than function-scoped var variables, which stay alive until the function returns.
Yes. A closure keeps a reference to its lexical environment. As long as the closure exists, the closed-over variables cannot be garbage collected. This is a common source of memory leaks.
Remove handlers when no longer needed, do not close over large objects unless necessary, use WeakRef or WeakMap where appropriate, and keep closures short-lived. Avoid accumulating closures that each keep a large object alive.
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