This allows the minifier to mangle the constants. It also allows the linter to find unused strings properly.

While at it, remove a few unused properties.

File                        Before      After       Diff
--------------------------------------------------------
bootstrap.bundle.min.js     22.09 kB    21.13 kB    -0.96 kB (-4.35 %)
bootstrap.min.js            15.4 kB     14.46 kB    -0.94 kB (-3.86 %)