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2022-07-28 23:59:00 【Endless cakes】

Class review 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title> class </title>
</head>
<body>
    <script type="text/javascript">
        /*
         summary ：
        1. Constructors in classes don't have to be written , To initialize an instance , If the specified attribute is added, write .
        2. If A Class inherited B class , And A The constructor is written in the class , that A In class constructors super It has to be called .
        3. Methods defined in class , They are all placed on the prototype object of the class , Called by an instance object of a class .
        
        */
        // Create a class 
        class Person{

            // Constructor method 
            constructor(name,age){
                this.name = name
                this.age = age
            }
            // General method 
            //speak Methods are placed on the prototype object of the class , For example 
            // adopt Person The instance speak when ,speak Medium this Namely Person example 
            speak(){
                console.log(` My name is ${this.name}, Age ${this.age} year `)
            }
        }
        // Create a  student class 
        class Student extends Person{
            constructor(name,age,grade){
                    super(name,age)
                    this.grade = grade
            }
            speak(){
                console.log(` My name is ${this.name}, Age ${this.age} year , I read ${this.grade} grade `)
            }
            study(){
                console.log(' I study very hard ')
            }
        }
        const s1 = new Student('xiaozhg',15,' higher ')
        s1.speak()
        s1.study()
    </script>
</body>
</html>
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