class Student {

    constructor(public name: string) { 
    }

    say() { 
        console.log(this.name + " saying");
    }
}

class HighSchoolStudent extends Student { 

    constructor(name: string, no: string) {
        super(name)
     }
    no:string;
    study() {
        super.say();
     }
}

var students: Array<Student> = [];
students[0] = new Student("zhangsan");
students[1] = new HighSchoolStudent("lisi","06169010");