Overview of JavaScript objects

An overview of JavaScript objects:

　　1, what is an object, is actually a type, that is, the reference type. The value of the object is an instance of the reference type.

2. A reference type in JavaScript is a data structure used to organize data and functionality together. It is also often called a class, but there is no such thing in JavaScript (impersonation).

3. Although JavaScript is an object-oriented language, it does not have the basic structure of classes and interfaces supported by traditional object-oriented languages.

4, in the application of storage and transfer of data, it is a very ideal choice.

　　

Second, the creation of JavaScript objects:

　　There are two types of Object creation. One is the use of the new operator, and the literal notation.

1. Create an object using the new operator

<script type= "Text/javascript" >   varnew Object ();        // an object   was created Alert (typeof box);            // Object Type  is objects      //　　Create an attribute field for an object] Box.name = ' Li Tinghui ';              　　=; Alert (// Get object's attribute field </script>

The new keyword can be omitted

<script type= "Text/javascript" >    var//          omit the new keyword = ' huang Jia Ai ' 　 　= a; Alert ("My name is" +box.name+ ", I Am" +box.age+ "year old ..."); </script>

　　　　2. Create objects using literal methods

<script type= "Text/javascript" >    var box =// create attribute field age:28　　}; Alert ("My name is" +box.name+ ", I Am" +box.age+ "year old ..."); </script>

Property fields can also be used as String forms

<script type= "Text/javascript" >    var box = {  // create attribute field ' age ':　　; Alert ("My name is" +box.name+ ", I Am" +box.age+ "year old ..."); </script>

Create objects by using literal methods, but you can use the traditional way when creating fields for objects

<script type= "Text/javascript" >   var box = {};     // literal method declares an empty object　　// traditional way to create field properties for an object box.age =;           　　alert (box.age); Alert ("My name is" +box.name+ ", I Am" +box.age+ "year old ..."); </script>

There are two ways to output a property

// dot notation Output // bracket notation Output, note the quotation marks

Iii. Creating methods for objects

 var  box = {run:  function  () {//  method in Object  return  ' run ' ; }} alert (Box.run ());  //  call method in Object  

function Objrun () {       return ' 123 ';    }    var New Object ();    = ' Euna lee '   =;    = Objrun ();      alert (box.age);   alert (box.run);

In the actual development process, we generally prefer the literal declaration method. Because it is clear, the syntax code is few, but also gives the person a kind of encapsulation feeling. Literals are also the preferred way to pass a large number of optional parameters to a function.

function // parameter is an object if　　(obj.name!=// determines if the attribute exists  if (obj.age! = undefined) alert (obj.age); }  var obj=' Li Tinghui ' , Box (obj);　　　　　　　　

Delete Object properties using Delete

    var box == ' Orient card ';　　} alert (Box.name);　　 Delete  box.name; alert (box.name); // has been deleted, undefined

Four, the object analysis:

　　1. What elements are included in the object

properties (Fields) method (function)

<script type= "Text/javascript" >varbox =NewObject ();//An object was createdAlerttypeofbox);//object type is objects      //create an object's properties (field)Box.name = ' Li Tinghui '; Box.age= 28; //Methods for creating objects (functions)    functionShow () {return"My name is" +box.name+ ", I Am" +box.age+ "year old .....; } alert (Show ()); //Get property fields for an object</script>

Simulate the map collection using the literal method:

             var oMap = {                8: "Xiao Qiang", 3: "Wang Choi", 7: "Xiao Ming"            }//            var val1 = omap[8]; //            alert ("Val1:" +val1);                        var val2 = Get (7); //             alert ("Val2:" +val2);                        function get (key) {                return  Omap[key];            }

An overview of JavaScript objects