TIL that Javascript engines optimize out unused variables available in outer lexical environment if they aren't used inside nested functions.
Earlier I used to think this is the default Spec behaviour but it's rather an optimization 💡.
In this video, we see how exactly Firefox confirms that for us !!
Top comments (2)
People really underestimate the power of JS engines, and what you pinpointed in this video is just a spec in a sea of optimizations within those engines. They all utilize cutting edge of optimization techniques, and this example with closures is not new.
Anyway, good video.
Thanks for sharing 🙌