Constructor function

Object can be also be created with the following two steps :

1. By writing a constructor function, define the object type. It would be better if we use a capital initial letter.
2. create an instance of obj with new.

To define an object type, create a function for the object type with its specified name, properties and its method. For example :

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

this keyword is to assign values to the object properties based on the value which we have passed to it to the function.

Now, create an object called humans :

var humans = new Person('ram',20,'male');

This creates humans and assign it to the properties with the specified values.

To retrieve these values : humans.name // "ram"
                                         humans.age // 20
                                         humans.gender // "male"

If we want to redefine the object Person. we can add the properties.

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

var details = new Person('sita',20,female,Hyderabad);

To retrieve these properties : 

details.name // "sita"

details.age // 20

details.gender // female

details.city // Hyderabad

we can always add a property for a previously defined object. For example

details.study = "B.E";

Adds this property to the details object and this doesn't effect the other object.