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     23.61 kB    22.61 kB    -1.00 kB (-4.23 %)
bootstrap.min.js            17.04 kB    16.08 kB    -0.96 kB (-5.63 %)