var person = {
    _name: "Mykola",
    bday: 8
};

Object.defineProperty(person, "name", {
    get: function() {
        return this._name;
    },
    set: function(newValue){
        if(newValue !== this._name) {
            this._name = newValue + " modified by setter";
            this.bday = bday + 1;
        }
    }
});

person.name = "Steven";
console.log(person.name);