What's the best way to build a function with prototypically inherited properties which still evaluates to typeof => 'function'?

gistfile1.js

var proto = {foo: true}

var f1 = Object.create(proto, function () { return 1 })
f1()   // => 1
f1.foo // => true
       // :)
typeof f1 // => 'object' 
          // :(

var f2 = function () { return 2 })
f2.__proto__ = proto // :(
f2()      // => 2
f2.foo    // => true
typeof f2 // => 'function'
          // :)

// is there a way without using __proto__?

Hmm. The problem with f2 is that it's now not instanceof Function, which also means it doesn't have the methods in Function.prototype. When I try proto = Object.create(Function.prototype, {}) strange things happen. Unfortunately I don't have time to fully understand what I'm seeing now, and I get the intuition that I'm "doing it wrong".