Debounce vs throttle — implement debounce

Question presented to candidate: "Implement a debounce function from scratch. Walk me through why it works, then show me it actually collapsing a burst of rapid calls into one."

What a strong answer should cover:

• A closure holding a single timer id across calls.
• Every call clears the previous pending timer, then starts a brand-new one — this is the entire mechanism.
• The wrapped function only actually runs once no new call has arrived within the delay window, and it runs with the arguments from the LAST call, not the first.
• Correct this handling if the debounced function needs to be used as a method (use a regular function for the wrapper and fn.apply(this, args), not an arrow function, if the caller relies on dynamic this).
• Real verification: proving with actual timestamps that a rapid burst produces exactly one effect call, not an assumption from reading the code.

Clarifying questions expected:

• "Should the debounced function support being called as an object method (i.e. does this need to work), or is a plain top-level function enough?"
• "Do you want a .cancel() method as part of this, or is that a separate follow-up?" (confirms scope — the advanced .cancel() variant is a distinct question in this bank)

Code / implementation expected: Yes — a full working debounce implementation, executed with a rapid-fire burst and real observed timestamps proving only the last call's effect fires.