Debounce II

You've built a basic debounce that defers a call until the user stops triggering events for wait milliseconds. In real applications you almost always need two more controls on top of that: a way to throw the pending call away, and a way to run it right now instead of waiting. Your job is to extend debounce so the returned function carries cancel() and flush() methods that do exactly that.

Signature

function debounceIi(
  fn: (...args: any[]) => any,
  wait: number
): {
  (...args: any[]): void;
  cancel(): void; // abort any pending invocation; fn is NOT called
  flush(): void; // invoke any pending invocation immediately; no-op if nothing is pending
};

The returned value is a function. cancel and flush are properties attached to that function.

Examples

// 1) cancel() throws away the pending call
const d = debounceIi(console.log, 100);
d('hello');
d.cancel();
// 100ms later: nothing prints. The pending call was discarded.

// 2) flush() runs the pending call right now with the latest args
const d = debounceIi(console.log, 1000);
d('a');
d('b');
d.flush(); // prints 'b' immediately — does NOT wait the remaining ~1000ms
d.flush(); // no-op: nothing is pending anymore

Notes

• Pending means scheduled-but-not-fired. A call is pending from the moment you invoke d(...) until the timer fires (or cancel/flush resolves it).
• cancel before any call is a no-op. cancel after the timer fires is a no-op. Never throws.
• flush with nothing pending is a no-op — fn must NOT be invoked. Same after a prior flush or cancel.
• flush uses the most recent args — exactly the args that the timer would have used.
• After flush or cancel, the debounced function is reusable. A fresh call after either should schedule a new pending invocation as normal.
• Preserve this — if the user attaches the debounced function as an object method (obj.save = debouncedIi(...)) and calls obj.save(), the eventual fn invocation should see obj as its this.