[btown]

I recently saw a code example in the VSCode repository where Extract was used in a really awesome way. Say you have a complex class with lots of fields and methods, and you want something that's a specifier for either a constructor's parameter or a query system. Often times, that will be very similar to the underlying class, but just the fields in it - excluding every member that's not a function. Instead of rewriting every single field name for your new type, just have your new type be Exclude<MyType, Function> or Partial<Exclude<MyType, Function>> and the resulting type is perfect for your needs.

Pick is also really useful if you have an interface that passes down a subset of complex things you get from a library; no need to retype their types, just extend a Pick of the library type.

In short, utility types are awesome!