addEventListenerkeydown

addEventListenerkeydown is a reference to registering a listener for the keydown event on a DOM element using the addEventListener method. The keydown event occurs when a key is pressed down on the keyboard while the element has focus, and it can fire repeatedly if the key is held.

The typical usage is element.addEventListener('keydown', listener, options). The listener is a function that receives a KeyboardEvent object with information about the key interaction. The options parameter can be a boolean or an options object; as an object it may include capture, once, and passive properties to control how the listener is invoked.

The KeyboardEvent object provides details such as event.key (the character or action, e.g., 'a', 'Enter'), event.code (the physical key, e.g., 'KeyA', 'Enter'), and modifier flags like event.altKey, event.ctrlKey, event.shiftKey, and event.metaKey. The repeat property indicates if the keydown event is an auto-repeat due to holding the key. For accessibility and IME scenarios, other properties may be present, and some browsers may differ in behavior for certain keys.

Common use cases include implementing keyboard shortcuts, validating or handling form input, and controlling UI actions via keyboard. It is important to consider focus context, as key events are typically captured by the element with focus; you can inspect event.target to tailor behavior accordingly, and call event.preventDefault() to override default browser behavior when appropriate.

Listeners should be removed with removeEventListener using the same event type and function reference to avoid memory leaks. addEventListener supports a wide range of elements and global targets like window and document, making keydown handling versatile across web applications.