Javascript notes-several methods for defining objects

Several Methods for defining objects in JavaScript (JavaScript does not have the concept of classes, but only objects ):

1) Expand its attributes and methods based on existing objects:

VaR object = new object ();

Object. Name = "zhangsan ";
Object. sayname = function (name)
{
This. Name = Name;
Alert (this. Name );
}

Object. sayname ("Lisi ");

2) Factory method

// Create an object in factory Mode

Function Createobject ()
{
VaR object = new object ();

Object. Username = "zhangsan ";
Object. Password = "123 ";

Object. Get = function ()
{
Alert (this. username + "," + this. Password );
}

Return object;
}

VaR object1 = Createobject ();
VaR object2 = Createobject ();

Object1.get ();

Construction Method with Parameters:

Function Createobject (username, password)
{
VaR object = new object ();

Object. Username = username;
Object. Password = password;

Object. Get = function ()
{
Alert (this. username + "," + this. Password );
}

Return object;
}

VaR object1 = Createobject ("zhangsan", "123 ");
Object1.get ();

Share a function object with multiple objects, rather than having one function object for each object.

FUnction get ()
{
Alert (this. username + "," + this. Password );
}

Function Createobject (username, password)
{
VaR object = new object ();

Object. Username = username;
Object. Password = password;

Object. Get = get;

Return object;
}

VaR object = Createobject ("zhangsan", "123 ");
VaR object2 = Createobject ("Lisi", "456 ");

Object. Get ();
Object2.get ();

3) constructor Method

Function person ()
{
// Before executing the first line of code, the JS engine will generate an object for us
This. Username = "zhangsan ";
This. Password = "123 ";

This. getinfo = function ()
{
Alert (this. username + "," + this. Password );
}

// There is a hidden return statement used to return the previously generated object.
}

VaR person = new person ();
Person. getinfo ();

You can pass parameters when constructing objects.

Function person (username, password)
{
This. Username = username;
This. Password = password;

This. getinfo = function ()
{
Alert (this. username + "," + this. Password );
}
}

VaR person = new person ("zhangsan", "123 ");
Person. getinfo ();

4) Prototype

// Create an object using prototype
Function person ()
{

}

Person. Prototype. Username = "zhangsan ";
Person. Prototype. Password = "123 ";

Person. Prototype. getinfo = function ()
{
Alert (this. username + "," + this. Password );
}

VaR person = new person ();
VaR person2 = new person ();

Person. Username = "Lisi ";

Person. getinfo ();
Person2.getinfo ();

*****************

Function person ()
{

}

Person. Prototype. Username = new array ();
Person. Prototype. Password = "123 ";

Person. Prototype. getinfo = function ()
{
Alert (this. username + "," + this. Password );
}

VaR person = new person ();
VaR person2 = new person ();

Person. username. Push ("zhangsan ");
Person. username. Push ("Lisi ");
Person. Password = "456 ";

Person. getinfo ();

Person2.getinfo ();

If a prototype object is used, all generated objects share the attributes in the prototype,

Such an object changes this attribute and is also reflected in other objects.

An object defined by prototype alone cannot assign an initial value to the attribute in the constructor. The attribute value can only be changed after the object is generated.
Define objects using prototype + constructor. Attributes of objects do not interfere with each other. Each object shares the same method.

// Define objects using prototype + Constructor

Function person ()
{
This. Username = new array ();
This. Password = "123 ";
}

Person. Prototype. getinfo = function ()
{
Alert (this. username + "," + this. Password );
}

VaR P = new person ();
VaR P2 = new person ();

P. username. Push ("zhangsan ");
P2.username. Push ("Lisi ");

P. getinfo ();
P2.getinfo ();

5) Dynamic Prototype: In the constructor, all objects share a method with the flag, and each object has its own attributes.

Function person ()
{
This. Username = "zhangsan ";
This. Password = "123 ";

If (typeof person. Flag = "undefined ")
{
Alert ("invoked ");

Person. Prototype. getinfo = function ()
{
Alert (this. username + "," + this. Password );
}

Person. Flag = true;
}
}

VaR P = new person ();
VaR P2 = new person ();

P. getinfo ();

P2.getinfo ();