/* array literal */
var aData = [];

/* object constructur */
function Person(firstname, lastname) {
  this.firstname = firstname;
  this.lastname = lastname;
  this.fullname = function() {
    return (this.firstname + " " + this.lastname);
  };
}

/* store object into array */
aData[aData.length] = new Person("Java", "Script"); // aData[0]

aData.push(new Person("Jhon", "Doe"));
aData.push(new Person("Anna", "Smith"));
aData.push(new Person("Black", "Pearl"));

aData[aData.length] = new Person("stack", "overflow"); // aData[4]

/* loop arrray */
for (var i in aData) {
  alert(aData[i].fullname());
}

/* convert array of object into string json */
var jsonString = JSON.stringify(aData);
document.write(jsonString);