JavaScript Object-oriented (i)

1 //VI: Object-oriented Programming2 //What is an object: "A collection of unordered attributes, they can contain basic values, objects, or functions", strictly speaking, is equivalent to a set of values that have no particular order, each object and method has a specific name,3 //each name is mapped to a value. 4 //Each object is created based on a reference type. 5 6 //attribute types (attributes): Data properties and properties that access their properties are attributes to the Jsvascript engine, so they are not accessed directly7 //1. Data Properties8 //[[[Configurabale]]: Indicates whether the Delete property can be deleted to redefine the property, whether the attribute can be modified or whether the property can be modified to access9 //its properties:Ten //[[[Enumerable]]: Indicates the ability to iterate through for-in One //[[writeble]]: Ability to modify the value of a property A //[[value]]: Save the value of the property -  - //To modify the properties of the above attributes, the Object.defineproperty () method specified in ECMAScript 5 must be used; This method accepts three parameters the //The ① property contains the name of the object ② property ③ A Descriptor object, and the descriptor attribute must be one or more of the above four -  -     varperson = {}; -Object.defineproperty (person, "name",{ +         //Configurable:false, -Writable:false, +Value: "Zhd" A     });  atPerson.name = ' Qi ';//due to the writable mark, at this time is illegal browser will ignore the execution of this sentence, strict mode error -     //Delete person.name; As configurable this operation is also illegal -alert (person.name);//Zhd -  -     //and once you mark configurable = False, you cannot change configurable to False by Object.defineproperty (), -     //once it is defined as a non-configurable type, it cannot be changed to a configurable type, at which point the call to Object.defineproperty () modifies the except writable in     //, there will be an error.  -     //This means that you can modify the same property multiple times by calling Object.defineproperty (), but when configurable is set to Flase, there is to     //Limit +     //when you call the Object.defineproperty () method, the default is False if you do not specify Configurable,writable,enumerable -     //(the default is true when creating objects) the  *     //2. Accessor properties (getter/setter) $     //[[Configurabale]: Indicates whether the Delete property can be deleted to redefine the property, or whether the attribute can be modified or can be modified to an accessor property:Panax Notoginseng                         //properties defined directly on the object, so the property value defaults to True -     //[[[Enumerable]]: Represents the ability to iterate through for-in directly on the object defined properties, so the property value defaults to True the     //[[Get]]: Read property value defaults to undefined +     //[[Set]: Write property value defaults to undefined A     //accessors can also use only Object.defineproperty () to set the     varBook = { +_year:2016,//① -Edition:1 $     }; $Object.defineproperty (book, ' Year ',{ -Getfunction() { -             return  This. _year;//② the         }, -Setfunction(newvalue) {Wuyi             if(NewValue > 2016){ the                  This. _year = newvalue;//③ -                 //Console.log (Newvlaue); Wu                  This. edition + = newValue-2016; -             } About         } $     }); -Book.year = 2017; -     //book._year = 2016;//browser will directly ignore -alert (book.year);//  Aalert (book.edition);//2 means that you can also change the values of other properties while setting a property +  the     //do not forget ②②③ "_", after forgetting to appear Maximum call stack size exceeded error.  -     //"_" is used to represent the property that can only be accessed through the object method _year to the Data property year for the accessor property $     //direct access to attributes with "_", the browser will directly ignore the the     //provides an accessor type with a Java private variable, but instead accesses the Get/set method to the year property in place of the _year the     //Java: the     //int GetYear () {return _year;} Person.getyear () ==> person.year; the     //void setyear (int value) {this._year = value;} Person.setyear (2) ==> person.year = 2; -     //You do not have to specify the Get/set method: The property is read-only when only get, and only if set, the property can only write in     //There are also two old methods: theBOOK.__DEFINEGETTER__ ("Year",function () { the         return  This. _year; About     }); theBOOK.__DEFINESETTER__ ("Year",function(newvalue) { the         if(NewValue > 2016){ the              This. _year =newvalue; +              This. edition + = newValue-2016; -         } the     });Bayi      the     //define multiple attributes (Get/set can also be defined directly within the function body) the     varBook = {}; - object.defineproperties (book,{ - _year:{ thevalue:2016 the         }, the edition:{ theValue:1 -         }, the year:{ theGetfunction(){ the                 return  This. _year;94             }, theSetfunction(newvalue) { the                 if(NewValue > 2016){ the                      This. _year =newvalue;98                      This. edition + = newValue-2016; About                 } -             }101         }102     });103 104  the     //reads an attribute of an object property returns a value when an object106     //if it is a data attribute, then there is configurable,enumerable,writable and value107     //if the accessor property is Configurable,enumerable,set and get108     //Accessing Data Properties109     varDescriptor = object.getownpropertydescriptor (book, "_year"); thealert (Descriptor.value);// .111alert (descriptor.configurable);//false the     //alert (type Descriptor.get);//"Undefined"113     //Access accessor Properties the     varDescriptor = object.getownpropertydescriptor (book, ' Year '); thealert (Descriptor.value);//undefined thealert (descriptor.enumerable);//false117AlerttypeofDescriptor.get);//"function"118alert (descriptor.get);//will return code

JavaScript Object-oriented (i)