Board Events

The onEvent block helps your app know when something happens, like when someone clicks a button or moves the mouse. The Circuit Playground has a similar block called onBoardEvent() that watches for things happening on the board.

In Event-Driven programming, remember that:

• People make events happen - Events happen when someone uses the buttons, switches, or other parts on the board.
• Events make code run - When an event happens, it can make a certain function work.

onBoardEvent

The onBoardEvent() block is a special kind of function called an Event Listener. It makes it easy to set up event handling with just one command. Here's an example with labels:

1. When the left button, buttonL, is clicked, the word "click" will appear on the screen. We use the variable buttonL (without quotation marks), which is different from onEvent that uses a string to name a design element.

2. This function doesn't have a name, and it's called a callback function. It's a bit strange because you don't use it directly in your code. Instead, the system calls the callback function when the event you chose happens. Callback functions are used a lot in event-driven programming.

Button Events

⚠️ A word of caution! The Circuit Playground and micro:bit buttons may look similar, but their names are slightly different:

• The Circuit Playground buttons are named buttonL and buttonR
• The BBC micro:bit buttons are named buttonA and buttonB