Question

Can someone clear up what I’m doing wrong with my code? I’m a total newb, simply trying to experiment with how to create objects, prototypes, and what the this command refers to in the context of prototypes. However, none of my code is working on jFiddle. I know this code is completely nonsensical, but I’m just trying to find out what the document prints in various cases to get a more concrete grasp of how objects, prototypes, constructors, and the “this” keyword works. But NOTHING is showing up at all!

function Person(identity) {
    this.identity = "fellow";
    this.logYou = function() {
        document.write('hi');
    };
};
Person.prototype.logMe = function() {
    document.write(this.identity);
};

var Dude = new Person("stud");

Person.logYou();  
Person.logMe();
Dude.logMe();

​

Answer 1

function Person() {
  this.identity = "fellow";
  this.logYou = function() {
    document.write('hi');
  };
};

When you call this.identity = "fellow"; the this keyword refers the context in which the function is running.
So if you call the function in the Global scope, this refers to window object:

Person();
alert(window.identity); // fellow

And if you instanciate the function, this keyword refers to the new object:

var Dude = new Person();
alert(Dude.identity); // fellow

So the function Person has no property identity.
If you want to have some property for your function:

Person.identity = "fellow";
alert(Person.identity); //  fellow