Javascript has almost become a required language for web developers nowadays, but many people only stop at some basic operation layers such as form verification. Currently, object-oriented languages are widely used, we need to learn the Object-Oriented Knowledge of javascript to better understand javascript and lay a solid foundation for a deep understanding of various Script frameworks. Javascript and java, C #, and other languages also have some object-oriented features. However, when comparing these features, we will find that these features are not really object-oriented, in many cases, the object itself is used to simulate object-oriented programming. Therefore, javascript cannot be regarded as an object-oriented programming language, but an object-based language.
In javascript, everything is really an object. new things are objects, methods are objects, and even classes are objects. The following describes the Object Features of objects, methods, and classes.
1. Let's take a look at the built-in Date.
The Code is as follows:
Var time = new Date ();
Var timeString = time. getFullYear () + "-" +
Time. getMonth () + "-" +
Time. getDate () + "" +
Time. getHours () + ":" +
Time. getMinutes () + ":" +
Time. getSeconds ();
Document. write (timeString );
You can use time to operate the referenced Date object. You can conveniently call a series of getXX () methods contained in the Date object to obtain information such as year, month, day, hour, minute, and second.
Let's take a look at the String.
The Code is as follows:
Var username = new String ("hello world ");
Document. write (username. length );
The variable username references the new String object and uses username to access the length attribute of the string object.
2. methods are also objects
The Code is as follows:
Function hello (){
Alert ("hello ");
};
Var helloRef = hello;
HelloRef ();
Hello is a method. helloRef is a variable that references the hello method. Both helloRef and hello point to the same method object. This means that helloRef can also be executed, helloRef (). Similarly, you can write the following code.
The Code is as follows:
Var helloRef = function (){
Alert ("hello ");
};
HelloRef ();
Function () {alert ("hello")} is an anonymous method. It is also an object. After using the helloRef variable to reference this method object, you can call the method through helloRef.
3. What about classes?Of course, classes are also objects. In javascript, unlike C # or java, class keywords are used to create classes. Instead, they are directly used to create classes or simulate classes.
The Code is as follows:
Function Person (username, age ){
This. Name = username;
This. Age = age;
This. Introduce = function (){
Alert ("My Name is" + this. Name + ", this year" + this. Age + "years old. ");
};
};
Var person1 = new Person ("James", 20 );
Person1.Introduce ();
The above creates a Person type with the construction parameters username and age. The created Person object can call the method Introduce contained in Person. Next, make some modifications to the code.
The Code is as follows:
Function Person (username, age ){
This. Name = username;
This. Age = age;
This. Introduce = function (){
Alert ("My Name is" + this. Name + ", this year" + this. Age + "years old. ");
};
};
Var PersonClass = Person;
Var person1 = new PersonClass ("James", 20 );
Person1.Introduce ();
Redeclare the new variable PersonClass and reference the Person class. Both PersonClass and Person point to the class referenced by the original Person, so you can also use PersonClass to create objects.
The above examples may not be very appropriate, but you can also have a look at all objects in javascript.
The next section details the objects in javascript.
