es2020 or higher.
It is also worth noting that IE still does not support optional chaining today, but if you do not have to support IE you should be fine.
I just want to know how this will apply for a long-term project with a big codebase.
In particular, how I will reduce transpiled code over time.
Thank you for your answer. Now it’s clear. Will use ‘target’ in tsconfig.
Just some friendly advice: avoid premature optimization. I would not worry about it too much unless it proves to be an actual issue.