class Test{
    constructor(a,b){
        this.a=a
        this.b=b
    }
    plus(){
        return this.a+this.b
    }
}

class Test1 extends Test{
    constructor(a,b){
       super(a,b)
    }

}

class Test2 extends Test{
    constructor(a,b){
       super(a,b)
    }

}
const test=new Test(1,2)
const test1=new Test(3,4)
console.log(test)
console.log(test1)

const res=new Test(1,2).plus()
const res1=new Test1(1,2).plus()
console.log(res)
console.log(res1)