keydown

El evento keydown es lanzado cuando una tecla es presionada (hacia abajo). A diferencia del evento keypress, el evento keydown es lanzado para las teclas que producen un carácter y también para las que no lo producen.

Información general

Especificación: DOM L3
Interfaz: KeyboardEvent
Burbuja: Si
Cancelable: Si
Objetivo: Document, Element
Acción: Varía: evento keypress; lanza el sistema de composición de texto; eventos blur y focus; DOMActivate evento; otro evento

Propiedades

Property	Type	Description
`target` Read only	EventTarget	The event target (the topmost target in the DOM tree).
`type` Read only	DOMString	The type of event.
`bubbles` Read only	Boolean	Whether the event normally bubbles or not
`cancelable` Read only	Boolean	Whether the event is cancellable or not?
`view` Read only	WindowProxy	`document.defaultView` (`window` of the document)
`detail` Read only	`long` (`float`)	0.
`target` Read only	EventTarget (DOM element)	Focused element processing the key event, root element if no suitable input element focused.
`char` Read only	DOMString (string)	The character value of the key. If the key corresponds to a printable character, this value is a non-empty Unicode string containing that character. If the key doesn't have a printable representation, this is an empty string. See key names and char values for the detail. Note: If the key is used as a macro that inserts multiple characters, this attribute's value is the entire string, not just the first character.
`key` Read only	DOMString (string)	The key value of the key represented by the event. If the value has a printed representation, this attribute's value is the same as the `char` attribute. Otherwise, it's one of the key value strings specified in Key values. If the key can't be identified, this is the string "Unidentified". See key names and char values for the detail. Read Only.
`charCode` Read only	Unsigned long (int)	The Unicode reference number of the key; this attribute is used only by the `keypress` event. For keys whose `char` attribute contains multiple characters, this is the Unicode value of the first character in that attribute. Warning: This attribute is deprecated; you should use `char` instead, if available.
`keyCode` Read only	Unsigned long (int)	A system and implementation dependent numerical code identifying the unmodified value of the pressed key. This is usually the decimal ASCII (RFC 20) or Windows 1252 code corresponding to the key; see Virtual key codes for a list of common values. If the key can't be identified, this value is 0. Warning: This attribute is deprecated; you should use `key` instead, if available.
`which` Read only	Unsigned long (int)	A system and implementation dependent numeric code identifying the unmodified value of the pressed key; this is usually the same as `keyCode`. Warning: This attribute is deprecated; you should use `key` instead, if available.
`location` Read only	long (float)	The location of the key on the device.
`repeat` Read only	boolean	`true` if a key has been depressed long enough to trigger key repetition, otherwise `false`.
`locale` Read only	string	The language code for the key event, if available; otherwise, the empty string.
`ctrlKey` Read only	boolean	`true` if the control key was down when the event was fired. `false` otherwise.
`shiftKey` Read only	boolean	`true` if the shift key was down when the event was fired. `false` otherwise.
`altKey` Read only	boolean	`true` if the alt key was down when the event was fired. `false` otherwise.
`metaKey` Read only	boolean	`true` if the meta key was down when the event was fired. `false` otherwise.

`preventDefault()` del evento `keydown`

Empezando desde Gecko 25, una llamada a preventDefault() del evento keydown impide la emisión del consiguiente evento keypress. Este es un comportamiento válido para la especificación D3E y otros navegadores importantes que se comportan de esta misma forma. Por otro lado, Gecko 24 y anteriores emiten el evento keypress aunque se haya llamado a preventDefault() del evento keydown predecesor. Aunque el atributo defaultPrevented del evento keypress sea true en este caso.

Eventos relacionados

Ejemplo

<!DOCTYPE html>
<html>
<head>
<script>

'use strict';

document.addEventListener('keydown', (event) => {
  const keyName = event.key;
  alert('keydown event\n\n' + 'key: ' + keyName);
});

</script>
</head>
<body>
</body>
</html>