Javascript DOM advanced programming 2.1 create reusable objects-I want to stick to it!

1. What does the object contain?

In JavaScript, functions and strings are actually objects.

• Inheritance

 //  Create an instance of the person object  VaR Penson = {}; Person. getname = Function  () {...}; Person. getage = Function  (){...};  // Create an instance of an emloyee object  VaR Employee = {}; Employee. gettitle = Function  () {...}; Employ. getsalary = Function  (){...};  //  Inherit methods from person objects Employee. getname = Person. getname; employee. getage = Person. getage;

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• Understanding object members

 
Ads. addevent (window, 'load ',Function() {Alert ('Document. Body is a: '+Document. Body );});//Document. Body is a: Object htmlbodyelementAds. addevent (window,'Load ',Function() {Alert ('Document. getelementbyid is a: '+Document. getelementbyid );});//Document. getelementbyid is://Function getelementbyid () {[native code]}
 

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• Everything in the window object (covering objects in the scope chain)

 
<H1> override the alert () method 
 

 

FunctionOverride (){//Override alert functionsVaRAlert =Function(Message) {window. Alert ('Overridden: '+Message) ;}; alert ('Alert');//Call the original Alert () function in the scope of the override () functionWindow. Alert ('window. Alert');} Override ();//Call the original Alert () in the window scope ();Alert ('alert from outside ');
 

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// Pop-up sequence: // overridden: Alert // window. Alert // alert from outside
 

• Understanding scopes and closures is fundamental

2. Create your own object

 

VaRMyobject =NewObject ();//An object is an object.VaRMyobject ={};//These two types have been instantiated. The instantiated object must be a constructor.//Create an arrayVaRMyarray =NewArray ();VaRAnotherobject =NewMyobject ();//Incorrect
 

• More and more: Create Constructor

 Function Myconstructor (){  //  Somecode  }  VaR Myconstructor = Function  (){  //  Comecode  }  VaR Myconstructor = New   Function ('A', '/* somecode */') //  Performance problems  // Use  VaR Myobject = New  Myconstructor ();  //  For example:  Function  Myconstructor (Message) {alert (Message );  This . Mymessage = Message ;}  VaR Myobject = New Myconstructor ('instantiating myobject' );  VaR Message = myobject. mymessage;

• Add static method

 //  Understanding the differences between instances and constructors helps eliminate many existing problems  //  ------- Only objects can run normally  //  Create an object instance  VaR Myobject = New  Object ();  //  Add an attribute Myobject. Name = 'jeff' ;  //  Add a method Myobject. alertname =Function  () {Alert (  This  . Name );}  //  Execute the Add Method  Myobject. alertname ();  //  Create an instance of a function object  VaR Myconctructor = Function  (){  //  Somecode  }  // Add a static property Myconstructor. Name = 'jeff' ; Myconstructor. alertname = Function  () {Alert (  This  . Name);} myconstructor. alertname ();  //  However, name and alertname will not be in the new instance  VaR Anotherexample = New  Myconstructor (); anotherexample. alertname ();  //  Not a function Error 

• Add static methods to the prototype

 
//Create ConstructorFunctionmyconstrctor (Message) {alert (Message );This. Mymessage =Message ;}//Add a public method (add at the underlying layer)Myconstructor. Prototype. clearmessage =Function(String ){This. Mymessage + = ''+String ;}//You can call this method on a new instance.VaRMyobject =NewMyconstructor ('Hello world! '); Myobject. clearmessage ();
 

Control access through private and privileged members (you only need to use common VaR and fuction keywords in this constructor)

 //  Create Constructor  Function  Myconstrctor (Message ){  This . Mymessage = Message;  //  Private attributes      VaR Separator = '-' ;  VaR Myowner = This  ;  // Private Method      Function  Alertmessage () {alert (myowner. Message );}  //  Information is displayed during instantiation;  Alertmessage ();}  //  If the following method is used, an error occurs. Myconstructor. Prototype. appendtomessage = Function  (String ){  This . Mymessage + = seqarator + string; //  Error undefined  } //  The privileged method must be defined using the this keyword in the scope of the constructor.  //  Create Constructor  Function  Myconstrctor (Message ){  This . Mymessage = Message;  //  Private attributes      VaR Separator = '-' ;  VaR Myowner = This  ; //  Private Method      Function  Alertmessage () {alert (myowner. Message );}  //  Information is displayed during instantiation;  Alertmessage ();  //  Privileged Methods      This . Appendtomessage = Function  (String ){  This . Mymessage + = separator + String; alertmessage ();}} //  At this time, you can  VaR Myobject = New Myconstructor ('Hello world' ); Myobject. appendtomessage ( 'Jeff' );  //  However, you still cannot use the following method: Myobject. alertmessage (); //  Not found 

• Are common, Private, privileged, and static Members really so important?

 //  Create Constructor  Function Myconstrctor (Message ){  This . Mymessage = Message;  //  Private attributes      VaR Separator = '-' ;  VaR Myowner = This  ;  //  Private Method      Function  Alertmessage () {alert (myowner. Message );}  // Information is displayed during instantiation;  Alertmessage ();  //  Privileged Methods      This . Appendtomessage = Function  (String ){  This . Mymessage + = separator + String; alertmessage ();}}  //  Common Methods Myconstructor. Prototype. clearmessage = Function  (String ){  This . Mymessage ='' ;}  //  Static attributes Myconctructor. Name = 'jeff' ;  //  Static Method Myconstructor. alertname = Function  () {Alert (  This  . Name );} 

Remember the rules for a few days to ensure that you properly define the identities of all members:

• Because private and privileged members are inside the function. New words are taken to every instance of the function.
• A common prototype member is part of an object blueprint and is applicable to each instance of the object instantiated using the new keyword.
• Static members only use one special instance of an object.

 

• Object literal