Js-class inheritance

Let's review the methods implemented with functions Student :

function Student(name) {    this.name = name;}Student.prototype.hello = function () { alert(‘Hello, ‘ + this.name + ‘!‘);}

If you write with a new class keyword Student , you can write it like this:

 class student {constructor (name)    {this.name = name;  } hello () {alert ( ' Hello, ' + this.name +  '! '); }} 
 
          compare to find out,  The definition of class  contains the constructor   constructor   and the function defined on the prototype object  Hello () 
 
  Another great benefit of defining objects with  class  is that  inheritance is more convenient. , think of the amount of code we need to write from  Student  to derive a  primarystudent . Now, the intermediate object inherited by the prototype, the constructor of the prototype object, and so on, need not be considered, directly through the   extends   to implement: 
  

Class Primerestudent extends Student (name,grade) {    Constructor (Name,grade) {        super (name);        This.grade=grade;    }    Saygrade () {        return (' My grade is: ' + This.grade);}    }

Explanation: To want to inherit, must have extends,constructor, super (xxxx), we here, constructor constructor,name is we inherit, so want super (name)/* like Python */, Grade is the new parameter, so to This.grade=grade,

Asygrade is our own function, so declare it.

Js-class inheritance