tapahtumankäsittelijät

Tapahtumankäsittelijät, or event handlers, are fundamental components in programming that allow applications to respond to user actions or system events. These events can range from a user clicking a button to a network connection being established. When an event occurs, the system triggers a specific piece of code, known as an event handler, to execute.

The primary purpose of an event handler is to manage and react to these occurrences. For example, in a graphical user interface, clicking a "Save" button would trigger an event. The associated event handler would then execute the logic to save the current data. Similarly, in web development, a user typing into a text field can trigger an "input" event, and a corresponding event handler might be used to validate the input in real-time.

Event handlers are typically associated with specific objects or elements within an application. They define what actions should be taken when a particular event is fired on that object. This event-driven programming model is crucial for creating interactive and responsive software. Different programming languages and frameworks provide various mechanisms for defining and implementing event handlers, but the core concept remains consistent: bridging the gap between an event and a specific response.