Detailed explanation of the use of Object in javascript_javascript skills

Copy code The code is as follows:

function forEach(o){
var html="";
for(var i in o){
html = i "=" o[i] " ";
}
console.log(html);
console.log(o);
}

//1
//Object.create(proto)
//Object.create(proto,descriptors)
//Create an object using the specified prototype and properties
//Parameters:
//proto: The prototype of the newly created object, which can be null
//descriptors: an optional object that maps attribute names to attribute descriptors
//Return a newly created object, inherited from proto, and has the properties of descriptors.

Copy code The code is as follows:

var obj = Object.create({x:1,y:2},{
z:{value:3,writable:true,enumerable:true,configurable:true}
});
forEach(obj)
obj.z=5
console.log(obj)
console.log("============================================== ========")

//2
//Object.defineProperties(o,descriptors)
//Create or configure multiple properties of the object
//Parameters:
//o: The object on which to create or configure properties
//descriptors: Object that maps attribute names to attribute descriptors
//Return object o

Copy code The code is as follows:

Object.defineProperties(obj,{
a:{value:"a",writable:false,enumerable:true,configurable:true},
b:{value:"b",writable:false,enumerable:true,configurable:true}
})
forEach(obj);
console.log("============================================== ========")

//3
//Object.defineProperty(o,name,desc)
//Create or configure a property of the object
//Parameters:
//o: The object on which properties will be created or configured
//name: Name of the attribute to be created or configured
//desc: A property descriptor object describing the new property to be created or the modification of the existing property
//Return object o

Copy code The code is as follows:

Object.defineProperty(obj,"c",{value:"c",writable:false,enumerable:false,configurable:true})
forEach(obj);
console.log("============================================== ========")

//4
//Object.freeze(o)
//Set an object as immutable and will not affect inherited properties
//Parameters:
//o: Object to be frozen
//Return true|false

Copy code The code is as follows:

var p = {x:1,y:2}
Object.freeze(p);
p.x =2;
console.log(p);
console.log(Object.isFrozen(p)) //true, once frozen, it cannot be unfrozen
console.log("============================================== ========")

//5
//Object.getOwnPropertyDescriptor(o,name)
//Parameters:
//o: an object
//name: attribute name to be queried
//Query the characteristics of an attribute
//Return a property descriptor object for the specified property of the object. If the specified property does not exist, return undefined.
/*
An attribute descriptor is an ordinary JavaScript object that describes the characteristics of an object. There are two types of JavaScript attributes. Data attributes have a value and three properties: enumerable,
Writable, and configurable. Accessor properties have a getter and/or setter method, and enumerability.
Descriptor of data attribute:
{
value: any javascript value,
writable: true|false,
enumerable: true|false,
configurable:true|false
}
Descriptor of accessor property:
{
get: function or undefined: replace attribute value
set: function or undefined : replace writability
enumerable:true|false,
configurable:true|false
}
*/

Copy code The code is as follows:

var o5 = Object.getOwnPropertyDescriptor(obj,"c");
console.log(o5);
forEach(o5);
console.log("============================================== ========")

//6
//Object.getOwnPropertyNames(o)
//Return the name of the non-inherited attribute
//Parameters:
//o: an object
//Return a name containing all non-inherited properties of o, including non-enumerable properties. {enumerable:false}

Copy code The code is as follows:

var o6 = Object.getOwnPropertyNames(obj);
console.log(o6);
console.log("============================================== ========")

//7
//Object.getPrototypeOf(o)
//Parameters:
//o: an object
//Return the prototype of an object

Copy code The code is as follows:

var o7 =Object.getPrototypeOf(obj);
console.log(o7);
console.log("============================================== ========")

//8
//Object.hasOwnProperty(propname);
//Parameters:
//propname is a string containing the property name of the object
//Check whether a property is inherited
//Return true|false

Copy code The code is as follows:

console.log(obj.hasOwnProperty("x")); //=>false
console.log(obj.hasOwnProperty("z")); //=>true
console.log("============================================== ========")

//9
//Object.isExtensible(o);
//Determine whether new attributes can be added to an object
//Parameters:
//o: Object to be checked for scalability
//Return can be added as true|cannot be added as false
//Description: All objects are extensible when created until they are passed to Object.preventExtensions(o) Object.seal(o) or Object.freeze(o);

Copy code The code is as follows:

console.log(Object.isExtensible(obj)); // =>true
//Object.preventExtensions(obj)//Set it as non-extensible
//console.log(Object.isExtensible(obj)); //=>false
console.log("============================================== ========")

//10
//Object.isFrozen(o)
//Determine whether the object is immutable
//Parameters:
//o: Object to be checked
//If o has been frozen and does not change, it is true; otherwise, it is false;

Copy code The code is as follows:

console.log("============================================== ========")

//11
//object.isPrototypeOf(o)
//Determine whether the current object is the prototype of another object
//Parameters:
//o: All objects
//If object is the prototype of o, it is true. If o is not an object or object is not the prototype of o, it is false.

Copy code The code is as follows:

var o = new Object();
Object.prototype.isPrototypeOf(o) // true
Array.prototype.isPrototypeOf([1,2]) //true;
Object.prototype.isPrototypeOf(Function.prototype) //true
console.log("============================================== ========")

//12
//Object.isSealed(o)
//Determine whether an object's attributes can be added or deleted
//Parameters:
//o: Object to be checked
//If o is closed, it is true, otherwise it is false.
// An object is closed if new (non-inherited) properties cannot be added to it, and existing (non-inherited) properties cannot be removed.
//The commonly used method to close an object is Object.seal(o) or Object.freeze(o)

console.log("========================================== ===========")

//13
//object.keys(o)
//Return free enumerable property name
//Parameters:
//o: an object

Copy code The code is as follows:

console.log(Object.keys({x:1,y:2}) ) //=>[x,y]
console.log("============================================== ========")

//14
//Object.preventExtensions(o)
//Prohibit adding new attributes to an object
//Parameters:
// o: Extensible object to be set
//Once set to non-expandable, it can never be changed to expandable

console.log("========================================== ===========")

//15
//object.propertyIsEnumerable(propname)
//Check whether a certain attribute is visible in the for/in loop
//Parameters
//propname: a string containing the specified property name of the object
//If the object has a non-inherited property named propname, and the property is enumerable, return true.

Copy code The code is as follows:

var o15 = new Object();
o15.x = 15;
o15.propertyIsEnumerable("x"); //true;
o15.propertyIsEnumerable("y"); //false;
o15.propertyIsEnumerable("toString"); //false;
console.log("============================================== ========")

//16
//Object.seal(o)
//Prevent adding or removing properties of the object
//Parameters
//o: Object to be closed
//Return the closed parameter object o

//17
//Object.toLocaleString()
//Return the localized string identifier of the object
//The default toLocaleString() method provided by the Object class simply calls the toString() method.
//But please note that other classes (Array, Date, Number, etc.) each define their own version of this method. Used to perform localized string conversion. When defining your own class, you may also need to override this method.

//18
//object.toString()
//Define the string representation of an object
//In javascript programs, the toString() method is generally not frequently called. Generally, this method is defined in the object, and the system will automatically call it when needed to convert the object into a string.

//19
//Object.valueOf()
//The original value of the given object
//Return the original value associated with the specified object, if such a value exists. If there is no value associated with the changed object, return the object itself