javascript lesson 7

As we think of property in a object as a variable associated with an object.

methods in a object can be thought as functions associated with an object.

ex:
   obj.method = function(){

};

methods can be used to change property values.

if we want to use the method for other objects as well, for this we use 'this' keyword.

first we define a method

var setAge  = function(newage){
this.age = new(newage);
}

now we define our object

var obj = new Object();

obj.age = 22;
obj.setttingnewage = setAge;        //this acts as a placeholder, it will store whichever object called this
obj.settingnewage(23);             // method, so now whenever  we type obj.settingnewage(23), this.age
                                                   // in the method will refer to bob.age . here this holds obj, since obj called it.

***we can define objects inside objects in javascript.

I tried to create objects by 2nd method using 'new' keyword. here 'Object' is the constructor. it is already defined by javascript. Now i am learning that we can make custom constructors as well.

the Object function constructor creates a object with no properties and we have to manually add them.

so we create custom constructors instead.
ex:

function Person(name, age){
this.name = name;
this.age = age;
}

so now we have 'Person' constructor, we can create person objects much easily here

var bob = new Person("bob", 22);   // properties are already defined

we can also initialize properties inside a constructor not just define them.
ex:
function Person(name, age){
this.name = name;
this.species = "Homo Sapien";
}                // we initialized the property species here.

**** Not just properties, we can also define methods directly inside constructors.

**** I know object is just like string or integer just like any variables. like we have done a array of integer and strings, we can also make a array of objects

ex : var family = new Array();
       family[0] = new Person("sur",22);
       family[1] = new Person("bur",23);


arrays filled with objects will work just like arrays filled with strings or integers.

*** we can send objects as argument to a function, just like we send int or string as arguments

Math.PI -this func gives the value of pi