When many JavaScript objects of the same type need to be created, an “object type” can be be created using an object constructor function.

function Car(type, model, year) {
    this.autoType = type;
    this.autoModel = model;
    this.autoYear = year;
}

The new to create many new objects based on the object type.

const myNewCar = new Car("Maserati", "Quattroporte", 2019);
const myOldCar = new Car("Alfa Romeo", "Guilia", 2019);
const myOlderCar = new Car("Maserati", "Ghibli", 2016);

Adding a new property to an Object will be added only to that object. It will not be added to any other objects created by the object type.

myNewCar.autoColor = "white";

A value given to a property will be a default value for all objects created by the constructor.

function Car(type, model, year) {
    this.autoType = type;
    this.autoModel = model;
    this.autoYear = year;
    this.autoColor = "white";
}

A new property cannot be added to an object constructor.

Car.autoColor = "white"; // this will not work; the property will be "undefined"

The new property must be added using the constructor function prototype.

Car.prototype.autoColor = "white";

Methods can also be added to an object constructor.

function Car(type, model, year) {
    this.autoType = type;
    this.autoModel = model;
    this.autoYear = year;
    fullName: function() {
        return this.autoType + " " + this.autoModel; // this is a method stored as a property/value pair
    }
}

The new method will be added to myNewCar. Not to any other Car objects.

myNewCar.changeColor = function (color) {
    this.autoColor = color;
}

A new method cannot be added to an object constructor function.

The following will produce a TypeError.

Car.changeColor = function (color) {
    this.autoColor = color;
}

myNewCar.changeColor("red"); // TypeError: myMother.changeName is not a function

The new method must be added using the constructor function prototype.

Car.prototype.changeColor = function (color) {
    this.autoColor = color;
}

myNewCar.changeColor("red");

new Object()   // a new Object object
new Array()    // a new Array object
new Map()      // a new Map object
new Set()      // a new Set object
new Date()     // a new Date object
new RegExp()   // a new RegExp object
new Function() // a new Function object

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