JavaScript: JavaScript in AJAX supports the basics of object-oriented. In the idea of object-oriented Javascript, one of the core concepts is class. A class represents the abstraction of a class of things with similar properties. By instantiating a class, you can obtain an instance belonging to the class, that is, an object.
The method for defining a class in JavaScript is as follows:
Function class1 (){
// Class member definition and constructor
} |
Class1 is both a function and a class. It can be understood as a class constructor and is responsible for initialization.
Use the new operator to obtain an instance of a class
The new operator has been used to introduce basic objects. For example:
Create a Date object, and Date indicates the Date class, but this class is provided internally by JavaScript rather than user-defined.
The new operator is not only effective for internal classes, but also for user-defined classes. for class1 defined in the previous section, you can use new to obtain an instance:
Function class1 (){
// Class member definition and constructor
}
Var obj1 = new class1 (); |
Aside from the concept of classes, class1 is a function in the code form. Can all functions be operated using new? Yes, in JavaScript, functions and classes are a concept. When a new operation is performed on a function, an object is returned. If no class member is initialized in this function, an empty object is returned. For example:
// Define a hello Function
Function hello (){
Alert ("hello ");
}
// Obtain an object through a new function
Var obj = new hello ();
Alert (typeof (obj )); |
According to the running results, the hello function is executed, and obj also obtains an object reference. When a new function is used, this function is the constructor of the class. The code in this function is considered to initialize an object. Functions used to represent classes are also called constructors.
Use square brackets ([]) to reference object attributes and Methods
In JavaScript, each object can be considered as a collection of multiple attributes (methods). It is very easy to reference an attribute (method), such:
Object Name. Attribute (method) Name
It can also be referenced in square brackets:
Object Name ["attribute (method) Name"]
Note that the method name and attribute name here are a string, not the original vertex (? ), For example:
Var arr = new Array ();
// Add an element to the array
Arr ["push"] ("abc ");
// Obtain the length of the array
Var len = arr ["length"];
// Length of the output Array
Alert (len ); |
The execution result is displayed.
The above code is equivalent:
Var arr = new Array ();
// Add an element to the array
Arr. push ("abc ");
// Obtain the length of the array
Var len = arr. length;
// Length of the output Array
Alert (len ); |
This method of referencing attributes (methods) is similar to arrays, reflecting the property that JavaScript objects are a set of attributes (methods.
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