setting property as function in a constructor javascript

What you created is a getter/setter for name:

1. A getter is a function which returns a value associated with an object property.
2. A setter is a function which updates the value associated with an object property.

Getters and setters are useful for creating “derived properties” (i.e. properties which are derived from other properties). For example:

function Person(firstname, lastname) {
    this.firstname = firstname;
    this.lastname = lastname;
}

Person.prototype.fullname = function (fullname) {
    if (arguments.length < 1) return this.firstname + " " + this.lastname;
    var newname = fullname.split(" ");
    this.firstname = newname[0];
    this.lastname = newname[1];
    return fullname;
};

var person = new Person("Aadit", "Shah");

alert(person.firstname);
alert(person.lastname);
alert(person.fullname());

person.fullname("Chuck Norris");

alert(person.firstname);
alert(person.lastname);
alert(person.fullname());

In the above code fullname is a derived property. It is derived from firstname and lastname. As you can see, when I update fullname, I am also updating firstname and lastname. Hence getters and setters are useful in this case.

However a lot of people misuse getters and setters. For example:

function Warrior(name) {
    this.name = function (newName) {
        if (arguments.length >= 1)
            name = newName;
        return name;
    }
}

In this case there's no good reason to create a getter/setter for name because it is not a derived property. It's a misuse of getters/setters and all it does is make the code slower. Instead it should be implemented as:

function Warrior(name) {
    this.name = name;
}

Plain and simple.

Now consider:

Person.prototype.toString = function () {
    return "Hi! my name's " + this.name;
};

The reason this doesn't work is because this.name is a getter function. Hence you need to call it to get the actual value. Thus, it should be:

Person.prototype.toString = function () {
    return "Hi! my name's " + this.name();
};

Finally, newer versions of JavaScript have built in support for getters and setters:

function Person(firstname, lastname) {
    this.firstname = firstname;
    this.lastname = lastname;
}

Object.defineProperty(Person.prototype, "fullname", {
    get: function () {
        return this.firstname + " " + this.lastname;
    },
    set: function (fullname) {
        var newname = fullname.split(" ");
        this.firstname = newname[0];
        this.lastname = newname[1];
    }
});

var person = new Person("Aadit", "Shah");

alert(person.firstname);
alert(person.lastname);
alert(person.fullname);

person.fullname = "Chuck Norris";

alert(person.firstname);
alert(person.lastname);
alert(person.fullname);

This makes getters and setters look like normal properties. Such properties are called accessor properties.

Here your constructor function is Warrior and you can add new method toString to an existing prototype Warrior. Like this you can add.

Warrior.prototype.toString = function(){ // code goes here }

this.name is a function .so

Warrior.prototype.toString = function(){
     return "Hi! my name's "+this.name();
}

Using new keyword to create new objects from the same prototype

Warrior.prototype.toString = function(){
    return "Hi! my name's "+this.name();
}
myname = new Warrior("ur name");
console(myname.toString());