KeyboardEventKeyboardEvent objects describe a user interaction with the keyboard; each event describes a single interaction between the user and a key (or combination of a key with modifier keys) on the keyboard. The event type (keydown, keypress, or keyup) identifies what kind of keyboard activity occurred. Show Note: KeyboardEvent events just indicate what interaction the user had with a key on the keyboard at a low level, providing no contextual meaning to that interaction. When you need to handle text input, use the input event instead. Keyboard events may not be fired if the user is using an alternate means of entering text, such as a handwriting system on a tablet or graphics tablet. ConstructorKeyboardEvent() Creates a new KeyboardEvent object. ConstantsThe KeyboardEvent interface defines the following constants. Keyboard locationsThe following constants identify which part of the keyboard the key event originates from. They are accessed as KeyboardEvent.DOM_KEY_LOCATION_STANDARD and so forth. Keyboard location identifiers
PropertiesThis interface also inherits properties of its parents, UIEvent and Event. KeyboardEvent.altKey Read onlyReturns a boolean value that is true if the Alt (Option or on OS X) key was active when the key event was generated. KeyboardEvent.code Read onlyReturns a DOMString with the code value of the physical key represented by the event. Warning: This ignores the user's keyboard layout, so that if the user presses the key at the "Y" position in a QWERTY keyboard layout (near the middle of the row above the home row), this will always return "KeyY", even if the user has a QWERTZ keyboard (which would mean the user expects a "Z" and all the other properties would indicate a "Z") or a Dvorak keyboard layout (where the user would expect an "F"). If you want to display the correct keystrokes to the user, you can use Keyboard.getLayoutMap(). Returns a boolean value that is true if the Ctrl key was active when the key event was generated. KeyboardEvent.isComposing Read onlyReturns a boolean value that is true if the event is fired between after compositionstart and before compositionend. KeyboardEvent.key Read onlyReturns a DOMString representing the key value of the key represented by the event. KeyboardEvent.locale Read onlyReturns a DOMString representing a locale string indicating the locale the keyboard is configured for. This may be the empty string if the browser or device doesn't know the keyboard's locale. Note: This does not describe the locale of the data being entered. A user may be using one keyboard layout while typing text in a different language. Returns a Number representing the location of the key on the keyboard or other input device. A list of the constants identifying the locations is shown above in Keyboard locations. KeyboardEvent.metaKey Read onlyReturns a boolean value that is true if the Meta key (on Mac keyboards, the Command key; on Windows keyboards, the Windows key ()) was active when the key event was generated. KeyboardEvent.repeat Read onlyReturns a boolean value that is true if the key is being held down such that it is automatically repeating. KeyboardEvent.shiftKey Read onlyReturns a boolean value that is true if the Shift key was active when the key event was generated. MethodsThis interface also inherits methods of its parents, UIEvent and Event. KeyboardEvent.getModifierState()Returns a boolean value indicating if a modifier key such as Alt, Shift, Ctrl, or Meta, was pressed when the event was created. Obsolete methodsKeyboardEvent.initKeyEvent() Initializes a KeyboardEvent object. This was implemented only by Firefox, and is no longer supported even there; instead, you should use the KeyboardEvent() constructor. KeyboardEvent.initKeyboardEvent()Initializes a KeyboardEvent object. This is now deprecated. You should instead use the KeyboardEvent() constructor. Obsolete propertiesKeyboardEvent.char Read only Returns a DOMString representing 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. 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. Returns a Number representing 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. In Firefox 26 this returns codes for printable characters. Warning: This attribute is deprecated; you should use KeyboardEvent.key instead, if available. Returns a Number representing a system and implementation dependent numerical code identifying the unmodified value of the pressed key. Warning: This attribute is deprecated; you should use KeyboardEvent.key instead, if available. This property is non-standard and has been deprecated in favor of KeyboardEvent.key. It was part of an old version of DOM Level 3 Events. KeyboardEvent.keyLocation Read onlyThis is a non-standard deprecated alias for KeyboardEvent.location. It was part of an old version of DOM Level 3 Events. KeyboardEvent.which Read onlyReturns a Number representing 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 KeyboardEvent.key instead, if available. EventsThe following events are based on the KeyboardEvent type. They can be delivered to any object which implements GlobalEventHandlers, including Element, Document, and Window. In the list below, each event links to the documentation for the Document handler for the event, which applies generally to all of the recipients. keydownA key has been pressed. keyupA key has been released. Obsolete eventskeypress A key that normally produces a character value has been pressed. This event was highly device-dependent and is obsolete. You should not use it. Usage notesThere are three types of keyboard events: keydown, keypress, and keyup. For most keys, Gecko dispatches a sequence of key events like this:
Special casesSome keys toggle the state of an indicator light; these include keys such as Caps Lock, Num Lock, and Scroll Lock. On Windows and Linux, these keys dispatch only the keydown and keyup events. Note: On Linux, Firefox 12 and earlier also dispatched the keypress event for these keys. However, a limitation of the macOS event model causes Caps Lock to dispatch only the keydown event. Num Lock was supported on some older laptop models (2007 models and older), but since then, macOS hasn't supported Num Lock even on external keyboards. On older MacBooks with a Num Lock key, that key doesn't generate any key events. Gecko does support the Scroll Lock key if an external keyboard which has an F14 key is connected. In certain older versions of Firefox, this key generated a keypress event; this inconsistent behavior was bug602812. Auto-repeat handlingWhen a key is pressed and held down, it begins to auto-repeat. This results in a sequence of events similar to the following being dispatched:
This is what the DOM Level 3 specification says should happen. There are some caveats, however, as described below. Auto-repeat on some GTK environments such as Ubuntu 9.4In some GTK-based environments, auto-repeat dispatches a native key-up event automatically during auto-repeat, and there's no way for Gecko to know the difference between a repeated series of keypresses and an auto-repeat. On those platforms, then, an auto-repeat key will generate the following sequence of events:
In these environments, unfortunately, there's no way for web content to tell the difference between auto-repeating keys and keys that are just being pressed repeatedly. Auto-repeat handling prior to Gecko 5.0Before Gecko 5.0 (Firefox 5.0 / Thunderbird 5.0 / SeaMonkey 2.2), keyboard handling was less consistent across platforms. WindowsAuto-repeat behavior is the same as in Gecko 4.0 and later. MacAfter the initial keydown event, only keypress events are sent until the keyup event occurs; the inter-spaced keydown events are not sent. LinuxThe event behavior depends on the specific platform. It will either behave like Windows or Mac depending on what the native event model does. Note: Manually firing an event does not generate the default action associated with that event. For example, manually firing a key event does not cause that letter to appear in a focused text input. In the case of UI events, this is important for security reasons, as it prevents scripts from simulating user actions that interact with the browser itself. Example<!DOCTYPE html>
<html>
<head>
<script>
'use strict';
document.addEventListener('keydown', (event) => {
const keyName = event.key;
if (keyName === 'Control') {
// do not alert when only Control key is pressed.
return;
}
if (event.ctrlKey) {
// Even though event.key is not 'Control' (e.g., 'a' is pressed),
// event.ctrlKey may be true if Ctrl key is pressed at the same time.
alert(`Combination of ctrlKey + ${keyName}`);
} else {
alert(`Key pressed ${keyName}`);
}
}, false);
document.addEventListener('keyup', (event) => {
const keyName = event.key;
// As the user releases the Ctrl key, the key is no longer active,
// so event.ctrlKey is false.
if (keyName === 'Control') {
alert('Control key was released');
}
}, false);
</script>
</head>
<body>
</body>
</html>
Specifications
The KeyboardEvent interface specification went through numerous draft versions, first under DOM Events Level 2 where it was dropped as no consensus arose, then under DOM Events Level 3. This led to the implementation of non-standard initialization methods, the early DOM Events Level 2 version, KeyboardEvent.initKeyEvent() by Gecko browsers and the early DOM Events Level 3 version, KeyboardEvent.initKeyboardEvent() by others. Both have been superseded by the modern usage of a constructor: KeyboardEvent(). Browser compatibilityBCD tables only load in the browser Compatibility notes
See also
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