once(eventName, listener)

Registers a one-time listener that will be automatically removed after the first invocation.

Parameters:

• eventName (string) – Event name.
• listener (function) – Callback function.

Returns: The EventEmitter instance (supports chaining).

Example:

          
            1emitter.once("connect", () => console.log("Connected!"));3emitter.emit("connect"); // Logs: Connected!4emitter.emit("connect"); // No output
          
        

Edge Cases:

• The listener is removed immediately after execution.
• Safe to attach multiple once listeners to the same event.

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