JavaScript--Understanding the properties of an object

Note: This article has been modified longDescription: There are two types of properties in ECMAScript: Data properties and accessor properties. Property Descriptor 1. Data Property Description: When modifying or defining a property of an object, add some attributes to the property.

attribute name	Description	Default Value
Value	Set the value of a property	Undefined
Writable	Set whether a value can be modified	True
Enumerable	Indicates whether the property can be returned through a for-in or Obj.keys () loop.	True
Configurable	Indicates whether a property can be redefined by deleting it with delete Can I modify attributes of a property Can I modify properties to accessor properties	True

varObj= {    Test:"Hello"}//Object existing attribute added attribute descriptionObject.DefineProperty(obj,"Test",{    Configurable:true | false,    Enumerable:true | false,    value:Any type of value,    writable:true | false});the attribute description of the newly added property of the//objectObject.DefineProperty(obj,"NewKey",{    Configurable:true | false,    Enumerable:true | false,    value:Any type of value,    writable:true | false});

To Object.defineProperty Object.defineProperties add data properties with or without a function, the Object.create writable, enumerable, and configurable default values are false .

Properties created using object literals , the writable, enumerable, and configurable attributes default to True.

2. Accessor Property Description: Sets or gets the value of a property of an object.

attribute name	Description	Default Value
Get	Functions that are called when a property is read	Undefined
Set	Functions that are called when a property is written	True
Enumerable	Whether it can be enumerated (using for...in or Object.keys ())	True
Configurable	Indicates whether a property can be redefined by deleting it with delete Can I modify attributes of a property Can I modify the property to an accessor property (whether the target property can set the attribute again)	True

var obj = {};Object.defineProperty(obj, "newKey", {    get:function (){} | undefined,    set:function (value){} | undefined    configurable: true | false    enumerable: true | false});

Note: When a getter or setter method is used, it is not allowed to use the writable and Value properties ECMAScript 5 to manipulate property attributes in the method: 1. Object.defineproperty () Description: This method can only define one property

Grammar:

Object.defineProperty(obj, prop, descriptor)

Parameter list:

obj：必需。目标对象 prop：必需。需定义或修改的属性的名字descriptor：必需。目标属性所拥有的特性

return value:

传入函数的对象。即第一个参数obj

Example

varObj= {};//Object.defineproperty (object, property, property descriptor)Object.DefineProperty(obj, "Name", {    Get: function(){        return  This._name;  //Use the access attribute in get and set must add "_"    },    Set: function(Val){        if(Array.IsArray(Val)){             This._name =Val;        } Else{             This._name = "Not an array cannot be assigned a value";        }    },    Enumerable: true,       //Represents an enumerable    Configurable: true      //Whether the property can be deleted});//Object {get:function, set:function, Enumerable:true, configurable:true}Console.Log(Object.Getownpropertydescriptor(obj, ' name ')); obj.name = "111";Console.Log(obj.name);

2. Object.defineproperties () Description: This method is used to define multiple properties.

varObj= {};Object.defineproperties(obj, {    name: {        value: "Emil Chau",        writable: true    },     Age: {        value:  -,        writable: true    },    Sex: {        Get: function(){            return  This._sex;        },        Set: function(Val){            if(Val=== 1){                 This._sex = "Male";            }Else{                 This._sex = "female";            }        }    }});obj.Sex = 0;Console.Log(obj.Sex); //female

JavaScript--Understanding the properties of an object