Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript 1.2; HTML 4.0

Synopsis

<element onkeydown="handler" ... >
element.onkeydown

Description

The onkeydown property of an HTMLElement object
specifies an event handler function that is invoked when the user
presses a key over the element.

The initial value of this property is a function that contains the
JavaScript statements specified by the onkeydown
attribute of the HTML tag that defined the object. When an event
handler function is defined by an HTML attribute, it is executed in
the scope of element rather than in the
scope of the containing window.

In the Netscape 4 event model, the onkeydown
handler function is passed an Event object as an argument. In the IE
event model, no argument is passed, but the applicable Event object
is available as the event property of the Window
object that contains the element.

The character code of the key pressed is contained in the
which property of the Event object in Netscape and
in the keyCode property of the Event object in IE.
You can convert this keycode to a string with
String.fromCharCode( ). The modifier keys in
effect can be determined from the Event.modifiers
property in Netscape or with Event.shiftKey( ) and
related methods in IE.

In the Netscape event model, you can cancel processing of the
keystroke by returning false from this handler. In
the IE event model, you cancel processing by setting
Event.returnValue to false. In
IE, this handler may return an alternate keycode that is used in
place of the key actually pressed by the user.

You can often use the onkeypress event handler
instead of the onkeydown and
onkeyup handlers.

See Also

Event, HTMLElement.onkeypress; Chapter 19