Exercise: Build an Auction System

Task

Imagine you're building an online auction platform where participants can join, place bids, and leave as the auction progresses. This exercise will challenge you to use event-driven programming to simulate the auction, implementing features such as registering one bid listener per participant, dynamically removing listeners when participants leave, and tracking active bidders in real time.

You’ll program the auctioneer to announce the start of the auction, manage bids, and clean up listeners when the auction ends. As participants interact, their actions will trigger events, making this a dynamic, interactive system.

Requirements

The following requirements outline the key features and functionality you need to implement for a fully event-driven auction system.

• Announce the start of the auction:

  • Use the once method to ensure the auctioneer announces the start of the auction only once.

  • Include the auction item's name in the announcement.

• Participants join the auction:

  • Write a createBidder function to dynamically register each participant.

  • Each participant should have a separate listener for the bid event, registered through the createBidder function.

  • The createBidder function should also provide:

    • A placeBid function for the participant to place bids.

    • A withdraw function to remove the participant from the auction.

  • Ensure each participant's listener stays registered while active, but ignores their own bids (responds only to bids from others).

• Participants place bids:

  • Each bid must include the bidder's name and the bid amount.

  • Broadcast the bid to all other participants.

  • After each bid, display the total number of active participants using the listenerCount method.

• Participants withdraw:

  • Use the removeListener method to unregister the listener for a withdrawing participant.

  • After withdrawal, update and display the total number of active participants.

• End the auction:

  • Use the .once() method to announce the end of the auction.

  • Use the .removeAllListeners() method to clean up all listeners when the auction ends.

Simulated auction flow

The following flow demonstrates how the auction system should function, showcasing the sequence of events and participant interactions.