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当一个键被按下后会触发keydown 事件

General info

Specification
DOM L3
Interface
KeyboardEvent
Bubbles
Yes
Cancelable
Yes
Target
Document, Element
Default Action
Varies: keypress event; launch text composition system; blur and focus events; DOMActivate event; other event

Properties

Property Type Description
target 只读 EventTarget Focused element processing the key event, root element if no suitable input element focused.
type 只读 DOMString The type of event.
bubbles 只读 Boolean Whether the event normally bubbles or not
cancelable 只读 Boolean Whether the event is cancellable or not?
view 只读 WindowProxy document.defaultView (window of the document)
detail 只读 long (float) 0.
target EventTarget (DOM element) Focused element processing the key event, root element if no suitable input element focused.
char 只读 未实现 (查看 bug 680830) 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 未实现 (查看 bug 680830) 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 {{ anch("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 只读 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 只读 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 {{ anch("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 只读 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 只读 long (float) The location of the key on the device.
repeat 只读 未实现 boolean true if a key has been depressed long enough to trigger key repetition, otherwise false.
locale 只读 未实现 string The language code for the key event, if available; otherwise, the empty string.
ctrlKey 只读 boolean true if the control key was down when the event was fired. false otherwise.
shiftKey 只读 boolean true if the shift key was down when the event was fired. false otherwise.
altKey 只读 boolean true if the alt key was down when the event was fired. false otherwise.
metaKey 只读 boolean true if the meta key was down when the event was fired. false otherwise.

preventDefault() of keydown event

Starting with Gecko 25, a call of preventDefault() of keydown event prevents to dispatch following keypress event. This is valid behavior for D3E spec and the other major web browsers behave this way. On the other hand, Gecko 24 or earlier dispatched keypress event even if preventDefault() of preceding keydown event is called. Although the keypress event's defaultPrevented attribute was true in this case.

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