JS-oriented (based on) object programming

Introduction to JS-oriented (based on) object programming

to create an object for a template with a class (prototype object)

Zhang Lao tai cat Problem

//traditional method more troublesome
var cat1_name= "small white";
var cat1_age=3;
var cat1_color= "White";

Solution: Put the cat's attribute set, create a new data class (prototype Object/Class). Use object-oriented approach to solve the above problem. //
Here is a cat class

function Cat () {
}
//If you use
//cat ();//function
var cat1=new cat ();//class
// At this time CAT1 is an object (instance)
cat1.name= "Small white";
cat1.age=3;
cat1.color= "White";
From the above code we can see that the
properties of objects in//1.js can be dynamically added.
//2. property is not restricted.

Window.alert (cat1.name+cat1.age+cat1.color+cat1.hobby);/No defined object pops up undefined

Streamlined as follows:

There are five different ways to create objects:

Use constructors to define classes (prototype objects)

Example:

In JS everything is Object function Person
() {}
Window.alert (person.constructor);//class is also object, is created by function of the object
var a= New person ();
Window.alert (a.constructor);//a the constructor of the object instance
Window.alert (typeof a); What type of//a is

var b=123;
Window.alert (b.constructor);
Window.alert (typeof b);

var c= "123";
Window.alert (c.constructor);
Window.alert (typeof c);

How to tell if an object instance is a person type.

if (a instanceof person) {
	Window.alert ("A is person Ok1");
}

if (A.constructor==person) {
    Window.alert ("A is person ok2");
}

Two ways to access the properties of an object
function person () {}
var p1=new person;
P1.name= "shunping";
alert (p1.name);
Alert (p1["name"]);
var val= "na" + "Me";
Alert (P1[val]);

Run Result: 10 name small white name small white

Operation schematic diagram:

JS garbage collection mechanism:

Memory by the JS engine management, JS engine is a part of the browser

Number of references 0 content 0 garbage collection

Description of object reference problem-----diagram

①js passively frees object memory:

Passive embodiment even if the reference number is 0, and do not know when it will be recycled, may be insufficient memory time

JS free memory ①----passive
 function person () {}
 var a=new person ();
 a.age=10;
 A.name= "Xiao Ming";
 var b=a;
 B.name= "Small white";
 Window.alert (b.age+ "name" +b.name+ "name" +a.name);
So far, two of the contents of the heap are quoted
B=null;
Window.alert (a.age+ "name" +a.name);
Window.alert ("b.age=" +b.age);
At this time the reference
a=null;

②JS also provides a way to proactively free object memory: Delete

JS free memory ②----Active  Delete
function person () {};
var a=new person ();
a.age=10;
A.name= "Xiao Ming";
var b=a;
B.name= "Small white";
Window.alert (b.age+ "1 names" +b.name);
Delete a.age;//Remove the properties of object A (Cannot delete object, only delete attribute)
//a and B are pointing to the same place, so B.age will also be deleted.
Window.alert (b.age+ "2 Names" +b.name);

Run Result: xiaoming 200