These are similar to the server side formatters.
You should define these client side formatters in jQuery document ready function ideally.
I am unable to find many example posts right now. But there are many in the community.
4 I could find:
The syntax in example you have posted is something I have seen for the first time.
The syntax I have used most is as in link.. with 3 parameters..
Source Object Type
Custom Formatter Name
Function with Custom Parameters
These formatter, just like server side do not show up in the UI. You can use them in code view.
Server side formatter can now show up in the UI with the new custom-modules, but no similar option is available for client side yet.