4 methods of javascript class definition_js object-oriented

/*
Factory method --- Create and return specific types Factory function of the object
*/
function createCar(color,doors,mpg){
var tempCar = new Object;
tempCar.color = color;
tempCar. doors = doors;
tempCar.mpg = mpg;
tempCar.showCar = function(){
alert(this.color " " this.doors);
}
return tempCar;
}

/*
Constructor method --- The constructor looks a lot like a factory function
*/
function Car(color,doors,mpg){
this .color = color;
this.doors = doors;
this.mpg = mpg;
this.showCar = function(){
alert(this.color);
};
}
/*
Prototype method---Using the prototype attribute of the object, it can be regarded as the prototype on which new objects are created
*/
function Car(color,doors, mpg){
this.color = color;
this.doors = doors;
this.mpg = mpg;
this.drivers = new Array("nomad","angel");
}

Car.prototype.showCar3 = function(){
alert(this.color);
};

/*
Mixed constructor/ Prototype method --- Use constructors to define all non-function attributes of objects, and use prototype methods to define function attributes (methods) of objects
*/
function Car(sColor, iDoors, iMpg) {
this. color = sColor;
this.doors = iDoors;
this.mpg = iMpg;
this.drivers = new Array("Mike", "Sue");
}

Car.prototype.showColor = function () {
alert(this.color);
};
/*
Dynamic prototype method --- define non-function properties within the constructor, and Function properties are defined using prototype properties. The only difference is where the object methods are assigned.
*/
function Car(sColor, iDoors, iMpg) {
this.color = sColor;
this.doors = iDoors;
this.mpg = iMpg;
this. drivers = new Array("Mike", "Sue");

if (typeof Car._initialized == "undefined") {

Car.prototype.showColor = function () {
alert(this.color);
};

Car._initialized = true;
}
} //This method uses the flag (_initialized) to determine whether the prototype has been assigned any method.