Question

As I understand it, a Function’s prototype property is how you add methods/properties to all objects instantiated from that function.

So when I try something like this

function Person(){}
Person.prototype.saySomething = function(){ alert( "hi there" ); }

Person.saySomething();

I get the error “Person.saySomething is not a function”, which makes sense as Im not executing the function on a Person object instance.

But why than does running the below code work?

Function.prototype.sayHi = function(){ alert( "hi!" );}

Function.sayHi();

Answer 1

You have to create an instance of Person first:

new Person().saySomeThing();

Prototype methods/properties are only inherit when an instance of the constructor is created, via the new keyword.

Function.sayHi() works, because the Function constructor is also a function.