JS constant rework => reduce minified JS by 7.5% (6.3% gzipped)

Created by: pvdlg

Fixes #20011 (closed)

Improve JS minification:

	Minified size	Minified gain	Minified + zip size	Minified + zip gain
Before	46,653b	-	12,648b	-
After	43,121b	7.5%	11,851	6.3%
With #21715	37,526b	19.5%	11,278	10.8%

In addition it allows the JS linter to detect unused variables. For example this variable is defined but not used and the linter cannot detect it.