This is a stunning example of why I dislike and avoid arrow functions. What you call "cleaner" I call "painfully and aggravatingly cryptic".
Whilst the change in the "this" behavior is nice, the utter lack of code clarity caused by the removal of words like "function" and "return" in favor of "iconography" and "absolutely jack" does NOTHING to help with "code clarity" and if anything reeks of obfuscation. Same for the garbage output variable/template junk that I find far less clear than addition and know from experience in other languages is far, FAR less efficient on the back end.
It violates the "things should be as simple as need be, but no more" principle by a mile and a half; much less the entire reason high level languages exist as to be brutally frank? Assembly has a cleaner, clearer, and more useful syntax and mnemonics.
And for what? "Wah, wah, eye dunz wunna tiep" and things that if they would/should be in your code, would/should be handled by a pre-processor? (Not that I care for those monuments to stupid either)
When people talk about stuff like this making code "cleaner" or "easier to read" I genuinely have ZERO huffing clue what they're talking about; but to be fair I spent a decade working in Ada, programmed for 20+ years before I ever once had to deal with the train wreck of obfuscation that is C syntax, and say the exact same thing about the illegible acid-trip that is colour syntax highlighting.