JavaScript Create Object

Create Object with constructor
http://www.w3schools.com/js/js_objects.asp

function person(firstname,lastname,age,eyecolor)
{
    this.firstname=firstname;
    this.lastname=lastname;
    this.age=age;
    this.eyecolor=eyecolor;

    this.newlastname=newlastname;
}


function newlastname(new_lastname)
{
    this.lastname=new_lastname;
}

var myFather=new person("John","Doe",50,"blue");
var myMother=new person("Sally","Rally",48,"green");

myFather.newlastname("Gu");