Instead of doing this purely in the Gruntfile I usually put a `.jshintrc` file in the root and pass the path as a `jshintrc` option.  This also works nicely in editors like sublime because plugins will pick it up and highlight problems.

You can also create two different .jshintrc files, one for the node/server stuff and then a separate one in the client folder with browser specific options and globals defined in it.