function Timer() {
  this.seconds = 0;
  this.tick = () => { this.seconds++; };
  this.tickRegular = function () { this.seconds++; };
}

const t = new Timer();
const { tick, tickRegular } = t;
tick();

let regularResult;
try {
  tickRegular();
  regularResult = 'no error';
} catch (e) {
  regularResult = e instanceof TypeError;
}

console.log(t.seconds, regularResult);