SOURCE

class ABC
{
    mail = "gqsun@outlook.com";
    print()
    {
        console.log(this.name);

    }    
}

class BCD extends ABC{
    print()
    {
        super.print();
        console.log(this.age);        
    }

}

var b = new BCD();
b.name= 'gavin';
b.age = 12;
b.print();
console.log(b.mail);

function Person(age)
{
    this.name = "gavin";
    this.age = age;
    var innerName = "Gaivn_Inner";
    var innerAge = 13;
    function printInner()
    {
        console.log(innerName, innerAge)
    }
    return {
        print:printInner
    }
    
}
Person.prototype.print =function()
    {
        console.log(this.name, this.age);
    }

var aa = new Person(12);
aa.print();