[JavaScript] class

class Person {

constructor(name, first, second) {

this.name = name;

this.first = first;

this.second=second;

}

sum() {

return this.first+this.second;

}

}

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

kim.sum = function(){

return 'this : '+(this.first+this.second);

}

var lee = new Person('lee', 10, 10);

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

-> kim.sum() this : 30

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

-> lee.sum() 20