The vim-abolish plugin provides a
couple handy shortcuts for quickly coercing the casing of a variable.
For instance, if you have a variable in camel case and you want to change it
snake case, you can navigate over the variable and hit crs (e.g.
myFavoriteVariable -> my_favorite_variable).
Similarly, you can hit crc to change a variable to camel case.
It even has support for mixed case (crm) and uppercase (cru).
h/t Jake Worth