func-getter-setter.js

const sum = {
  current: 0,
  get result() {
    return `The current result is ${this.current}`;
  },
  set add(n) {
    if (typeof n === 'number') this.current = this.current + n;
  }
};

sum.add = 31;
sum.add = 7;
sum.add = 4;
console.log(sum.result); // The current result is 42