What is an object in coding that waits for events and responds to them called?

An object that waits for events and responds to them is commonly known as a listener. In programming, listeners are designed to monitor specific events, such as user interactions or changes in data, and trigger appropriate responses when those events occur. This enables developers to create dynamic and interactive applications where actions can be taken based on user input or other events.

Listeners provide a mechanism for decoupled communication within an application, allowing different parts of the program to work together efficiently. By having a dedicated listener object, developers can manage multiple events and responses in a structured manner, enhancing code organization and maintainability.

Other terms like event handler and callbacks are related but do not fully encapsulate the role of a listener. An event handler often refers specifically to the function that processes an event, while a callback is a more general term for a function passed into another function to be called later. The observer pattern can also involve listeners, but it is a broader concept related to how objects communicate about state changes. Thus, the term listener accurately represents the function of waiting for and responding to events in this context.