[JavaScript] 상속

class Person {

constructor(name, first, second) {

this.name = name;

this.first = first;

this.second=second;

}

sum() {

return this.first+this.second;

}

}

class PersonPlus extends Person {

avg() {

return (this.first+this.second)/2;

}

}

var kim = new PersonPlus('kim', 10, 20);

console.log("kim.sum()", kim.sum());

-> kim.sum() 30

console.log("kim.avg()", kim.avg());

-> kim.avg() 15