Reading Notes for JavaScript advanced programming (13): defining classes or objects

Factory method

Create and return specific types of objects.

 
FunctionCreatecar (scolor, idoors, impg ){
VaROtempcar =NewObject ();
Otempcar. Color = scolor;
Otempcar. Doors = idoors;
Otempcar. mpg = impg;
Otempcar. showcolor =Function(){
Alert (This. Color );
}
Return otempcar;
}
 

Call example:

 
VaROcar1 = createcar ("red", 4,23 );
VaROcar2 = createcar ("blue", 3,25 );
Ocar1.showcolor ();
Ocar2.showcolor ();
 

Disadvantage: The method is already created. For example, in the preceding call example, both ocar1 and ocar2 have their own shocolor methods, but they can be shared.

Constructor Method

Example:

FunctionCar (scolor, idoors, impg ){
This. Color = scolor;
This. Door = idoors;
This. Mpg = impg;
This. Showcolor =Function(){
Alert (This. Color );
}
}
 

Call example:

 
VaROcar1 =NewCar ("red", 4, 23 );
VaROcar2 =NewCar ("blue", 3, 25 );
 

Disadvantage: Same as the factory method, the method is created again.

Prototype

This method uses the prototype attribute of the object to view it as the prototype on which the object is created. Here, we use an empty constructor to set the class name. Then, all attributes and methods are directly assigned to the prototype attribute, and the previous example is rewritten,CodeAs follows:

FunctionCar (){
}

Car. Prototype. color = "red ";
Car. Prototype. Doors = 4;
Car. Prototype. mpg = 23;
Car. Prototype. showcolor =Function(){
Alert (This. Color );
}
 

Call:

 
VaROcar1 =NewCar ();
VaROcar2 =NewCar ();
 

Disadvantage: The parameter initialization attribute value cannot be passed to the constructor.

Hybrid constructor/prototype

The constructor and prototype are used in combination. The example is as follows:

FunctionCar (scolor, idoors, impg ){
This. Color = scolor;
This. Door = idoors;
This. Mpg = impg;
}

Car. Prototype. showcolor =Function(){
Alert (This. Color );
}
 

Call example:

 
VaROcar1 =NewCar ("red", 4, 23 );
VaROcar2 =NewCar ("blue", 3, 25 );
 

Advantage: no memory waste, easy to create.

This is the main method adopted by ecmascript.

Dynamic Prototype Method

By using a hybrid constructor/prototype, the object method is defined outside the object, which makes people feel that it is not so object-oriented and is not visually encapsulated, therefore, a dynamic prototype method is generated:

  function  Car (scolor, idoors, impg) {
  This . color = scolor; 
  This . door = idoors; 
  This . MPG = impg; 
  If  ( typeof  Car. _ initialized = "undefined") {
 Car. prototype. showcolor =  function  () {
 alert ( This . color); 
}; 
 Car. _ initialized =  true ;< BR >}