Javascript object-oriented Learning 1 function object

JavaScript programming has been around for a while, but there are still a lot of basic concepts that seem to be understandable. If you do not understand them, correct them.

1: function and Function

Code
Alert (function );
// Function function (){
// [Native code]
// }
Alert ( Typeof Function ); // Function
Alert (Function Instanceof Object ); // True

Function Fun (){};
Alert ( Typeof Fun ); // Function
Alert (fun. Constructor = Function ); // True
Alert (fun Instanceof Function ); // True
Alert (fun Instanceof Object ); // True

The built-in function of the function system, which is used to create user-defined functions. And they all "inherit" from objects.

2: function and Object

Code
Function Class (){};

Alert ( Typeof Class ); // Function
Alert (class. Constructor = Function ); // True
Alert (Class Instanceof Function ); // True
Alert (Class Instanceof Object ); // True
Alert ( Typeof Class. Prototype ); // Object

VaR C1 =   New Class ();
Alert ( Typeof C1 ); // Object
Alert (c1.constructor = Class ); // True
Alert (C1 Instanceof Class ); // True
Alert (C1 Instanceof Function ); // False
Alert (C1 Instanceof Object ); // True
Alert ( Typeof C1. _ PROTO __); // In IE, undefined Firefox is an object.
Alert (C1. _ PROTO __ = Class. Prototype ); // In IE, flase Firefox is true.

A function is an instance of a function. It inherits from an object. Besides the features of an object, it also has
1) You can perform the new operation to simulate some object-oriented functions. The new operation returns an object. It is an instance of constructors and object objects.
2) Three steps for the new class () Operation
A) var C1 = new object
B) Copy all the attributes and methods of the original function class to the new C1.
C) C1. _ PROTO _ = Class. Prototype
3) In C1, point this to C1
// _ PROTO __is not visible in IE, but corresponding hidden values should exist.

3: About instanceof in Javascript
Interesting to see an example in http://www.cnblogs.com/bmrxntfj/archive/2008/07/17/829833.html
Code
Function Class1 (){};
Function Class2 (){};
Class2.prototype =   New Class1 ();
Function Class3 (){};
Class3.prototype =   New Class2 ();
Function Class4 (){};
Class4.prototype =   New Class3 ();
Function Class5 (){};
Class5.prototype =   New Class4 ();

VaR OBJ =   New Class4 ();

// Test the normal inheritance relationship
Alert (OBJ Instanceof Class5 ); // False
Alert (OBJ Instanceof Class4 ); // True
Alert (OBJ Instanceof Class3 ); // True
Alert (OBJ Instanceof Class2 ); // True
Alert (OBJ Instanceof Class1 ); // True

Class3.prototype =   New Class5 (); // Change the inheritance relationship

// Test the inherited relationship after the change
Alert (OBJ Instanceof Class5 ); // False
Alert (OBJ Instanceof Class4 ); // True
Alert (OBJ Instanceof Class3 ); // False
Alert (OBJ Instanceof Class2 ); // True is still true
Alert (OBJ Instanceof Class1 ); // True is still true

Use the followingCodeThe test is only valid in Firefox.

 

Code
VaR _ PROTO = OBJ. _ PROTO __;

While (_ PROTO ){
If (_ PROTO = Class1.prototype ){
Alert ( " Class1 " );
}
Else   If (_ PROTO = Class2.prototype ){
Alert ( " Class2 " );
}
Else   If (_ PROTO = Class3.prototype ){
Alert ( " Class3 " );
}
Else   If (_ PROTO = Class4.prototype ){
Alert ( " Class4 " );
}
Else   If (_ PROTO = Class5.prototype ){
Alert ( " Class5 " );
}
Else   If (_ PROTO = Object. Prototype ){
Alert ( " Object " );
} Else {
Alert ( " Unknow " );
Alert (_ PROTO. constructor );
}
_ PROTO = _ PROTO. _ PROTO __;
}

Normal inheritance relationship
Class4-> class3-> class2-> class1-> Object

Inheritance relationship after change
Class4-> unknow-> class2-> class1-> Object

Instanceof compares nodes on the _ PROTO _ chain one by one. If an equal node is found, true is returned; otherwise, false is returned.

The _ PROTO. constructor of the unknow object is displayed as "function class1 (){}"
However, except for objects, class4 ~ The _ PROTO. constructor of class1 is "function class1 (){}"
I still don't quite understand this, but I really don't understand it. If you know it, give some advice.

Refer:
Http://www.javaeye.com/topic/155109
Http://www.cnblogs.com/bmrxntfj/archive/2008/07/17/829833.html
Http://blog.csdn.net/nksongzz/archive/2008/06/25/2585196.aspx