http://www.cnblogs.com/objectorl/archive/2010/01/11/Object-instancof-Function-clarification.html
构造器(自定义的或者系统默认的)是Function方法构造而出的,所以 function Foo() {}; var ifoo = new Foo();
// __proto__ __proto__ __proto__
// foo -----------> Foo.prototype -----------> Object.prototype -----------> null
// But foo is not an instance of Function, because
// we could not find Function.prototype in foo‘s
// prototype chain.
Foo instanceof Function;//true
ifoo instanceof Function;//false
Foo instanceof Object//true
ifoo instanceof Object//true
原文:http://www.cnblogs.com/Aladingding/p/5106697.html