close #8475
close #8504

close #4761

* refactor: replace `forEach` with `for`-loops

Changes:
* Most `Object.keys(o).forEach` are replaced by `for in`.
* Most `Array.filter(c).forEach` are replaced by `for of` + `if continue`.
* `return` in `forEach` callbacks are replaced by `continue`.

There may be minor improvement to memory footprint as this change would
reduce the creations of temporary arrays and temporary functions.

* fix: return -> continue

* refactor: remove the commented out code

close #6682

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Co-authored-by: Zoltan Kochan <z@kochan.io>