Another approach to this test: https://www.measurethat.net/Benchmarks/Show/3444/0/switch-vs-object-literal

Compares performance of using a 'switch' statement vs object functions and object properties

Now regex flies and split crawls. BTW that regex match split plus join is what jQuery's removeClass() does - just much worse. Had to double check just in case that there's some hidden trick involved.

unshift vs concat vs spread of another array

test

Using spread operator vs mutating accumulator in reduce loop