Challenge 2 — Solution

Task: Create an object counter with a count property (0) and a
method increment() that increases count by 1 and logs it. Extract
increment as a standalone function, use bind() to lock it to
counter, then call the bound version three times via setTimeout to
prove this stays correct even when called asynchronously.

const counter = {
    count: 0,
    increment() {
        this.count++;
        console.log(this.count);
    }
};

const boundIncrement = counter.increment.bind(counter);

setTimeout(boundIncrement, 100);
setTimeout(boundIncrement, 200);
setTimeout(boundIncrement, 300);


Expected output (over ~300ms):

1
2
3


Notes:
- counter.increment.bind(counter) returns a brand-new function with
  this permanently fixed to counter — calling boundIncrement on its
  own (the plain-call situation from this chapter) no longer loses
  this, because bind already locked it in beforehand.
- setTimeout calls boundIncrement as a plain callback, exactly the
  situation that breaks an un-bound method (Fundamentals Chapter 8's
  callback problem) — bind is specifically what prevents that here.
- All three calls update the SAME counter.count, since boundIncrement
  always refers back to the same counter object every time it runs.