Introduction to TS, constructor and its this, inheritance, abstract class and interface

Class

class Person{
    
    //  No, static Keywords are the attributes and methods of the instance , It can only be accessed and modified through instances 、 call 
    name: string = 'tm' // Equate to  name='tm'
    age: number = 18 // Equate to  age=18
    //  Yes readonly Keyword is a read-only property , Do not modify 
    // readonly age: number = 18
    sayHellow() {
    
        console.log('hellow');  
    }

    // Yes static Keyword is a class attribute ( Static attribute ) And class methods ( Static methods ), It can only be accessed and modified through the class name 、 call 
    static sex: string = ' Woman ' // Equate to  static sex=' Woman '
    // readonly When decorating class properties , Must be on static Back 
    // static readonly sex: string = ' Woman ' 
    static sayHellow() {
    
        console.log('static--hellow');  
    }
    
}

console.log(Person.sex);// Woman 
Person.sayHellow() //static--hellow


const person1 = new Person()
console.log(person1.name, person1.age); //tm 18
person1.sayHellow()//hellow

Constructor and its this

class Dog{
    
    name: string
    age: number

    // this Always point to the current instance object 
    constructor(name: string, age: number) {
    
        this.name = name
        this.age = age
    }

    // this Always point to the current call instance object  
    bark() {
    
        console.log(this.name);
    }
}

// Once the use new Create objects , Will call Dog Of constructor Method 
const dog1 = new Dog(' Little black ', 3) 
const dog2 = new Dog(' The small white ', 6)

dog1.bark() // Little black 
dog2.bark() // The small white 

Inheritance and abstract classes

//abstract Keyword decorated class is abstract class , Abstract classes are classes that are designed to be inherited , Can't be used to create objects 
abstract class Animal{
    
    name: string
    age: number

    constructor(name: string, age: number) {
    
        this.name = name
        this.age = age
    }

	//abstract The method of keyword modification is abstract method , Abstract methods have no method bodies , Abstract methods can only be defined in abstract classes , Subclasses must override abstract methods 
    abstract sayHellow():void
}

//  If used extends keyword , be Animal Parent class ,Dog Subclass ; It is equivalent to copying the properties and methods of the parent class into the child class 
class Dog extends Animal{
    
    //  Subclasses can also add methods and properties by themselves 
    sex: string

    constructor(name: string, age: number, sex: string) {
    
        super(name, age)// Call the constructor of the parent class 
        this.sex = sex
    }
    
	sayHellow() {
    
        console.log(' The dog is barking ');
    }  
    
    run() {
    
        console.log(' The dog is running ');
    }
}

class Car extends Animal{
    
    // Override of parent method 
    sayHellow() {
    
        console.log(' The cat is barking ');
    }  
}

const dog = new Dog(' Dogs ', 5, ' Woman ')
console.log(dog.sex); // Woman 
dog.sayHellow()// The dog is barking 
dog.run()// The dog is running 

const car = new Car(' Cat and cat ', 2)
car.sayHellow()// The cat is barking 

Interface

// All attributes in an interface cannot have actual values , All methods are abstract methods 
// Interface is mainly to define a certain standard , Restricted classes must meet this standard 
// Interface is ts Peculiar ,js There is no concept of interface in 
interface myInter{
    
	name: string
	sayHellow():void // The function does not return a value 
}

class MyClass implements myInter{
    
	name: string

	constructor(name: string) {
    
		this.name = name
    }
	
	sayHellow() {
    
		console.log('aaa')
	}
}