Detailed explanation of javascript attribute and method reference, addition and deletion of instances-JS Tutorial-php.cn

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Detailed explanation of javascript attribute and method reference, addition and deletion of instances

伊谢尔伦

Jul 21, 2017 pm 01:24 PM

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References to properties and methods

1) In terms of visibility:

Private properties and methods can only be referenced within the object.

Instance properties and methods can be used anywhere, but must be referenced through objects.

Class properties and methods can be used anywhere, but cannot be referenced through instances of objects (this is different from Java, in which static members can be accessed through instances).

2) From the object level:

is similar to the reference of Java beans and can be referenced in depth.

Several ways:

Simple property: obj.propertyName

Object property: obj.innerObj.propertyName

Index property: obj.propertyName[index ]

Similar to above for deeper references.

3) In terms of definition:

Attributes defined through index must be referenced through index.

Attributes defined through non-index methods must be referenced through normal methods.

Also note: Object methods cannot be defined through index.

Dynamic addition and deletion of attributes and methods

1) For an instantiated object, we can dynamically add and delete its attributes and methods. The syntax is as follows ( Assume that the object instance is obj):

Dynamicly add object properties

obj.newPropertyName=value;

Dynamicly add object methods

obj.newMethodName=method Or =function(arg1,…,argN){}

Dynamic deletion of object properties

delete obj.propertyName

Dynamic deletion of object methods

delete obj .methodName

2) Example:

function User(name){
 
this.name=name;
 
this.age=18;
 
}
 
var user=new User(“user1”);
 
user.sister=“susan”;
 
alert(user.sister);//运行通过
 
delete user.sister;
 
alert(user.sister);//报错：对象不支持该属性
 
user.getMotherName=function(){return “mary”;}
 
alert(user.getMotherName());//运行通过
 
delete user.getMotherName;
 
alert(user.getMotherName());//报错：对象不支持该方法

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