What does return this in Function.prototype.method do? [duplicate]

Answer 1

It allows for chaining so you can do something like this:

/* ADD METHODS */
Person.method('getName', function() { return this.name; })
      .method('getAge', function() { return this.age; });

Answer 2

return this returns the object on which method() was called, and after it has been modified by adding the passed method to it.

Omitting it won't break your code, but it is a better style that allows chained method invocation, so you can for instance:

Person.method('getName', function() { return this.name; }).method('getAge', function() { return this.age; });