Английская Википедия:DOM event

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Шаблон:Multiple issues DOM (Document Object Model) Events are a signal that something has occurred, or is occurring, and can be triggered by user interactions or by the browser.[1] Client-side scripting languages like JavaScript, JScript, VBScript, and Java can register various event handlers or listeners on the element nodes inside a DOM tree, such as in HTML, XHTML, XUL, and SVG documents.

Examples of DOM Events:

  • When a user clicks the mouse
  • When a web page has loaded
  • When an image has been loaded
  • When the mouse moves over an element
  • When an input field is changed
  • When an HTML form is submitted
  • When a user presses a key[2]

Historically, like DOM, the event models used by various web browsers had some significant differences which caused compatibility problems. To combat this, the event model was standardized by the World Wide Web Consortium (W3C) in DOM Level 2.

Events

HTML events

Common events

There is a huge collection of events that can be generated by most element nodes:

  • Mouse events.[3][4]
  • Keyboard events.
  • HTML frame/object events.
  • HTML form events.
  • User interface events.
  • Mutation events (notification of any changes to the structure of a document).
  • Progress events[5] (used by XMLHttpRequest and File API[6]).

Note that the event classification above is not exactly the same as W3C's classification.

Category Type Attribute Description Bubbles Cancelable
Mouse click onclick Fires when the pointing device button is clicked over an element. A click is defined as a mousedown and mouseup over the same screen location. The sequence of these events is:
  • mousedown
  • mouseup
  • click
 Шаблон:Yes Шаблон:Yes
dblclick ondblclick Fires when the pointing device button is double-clicked over an element Шаблон:Yes Шаблон:Yes
mousedown onmousedown Fires when the pointing device button is pressed over an element Шаблон:Yes Шаблон:Yes
mouseup onmouseup Fires when the pointing device button is released over an element Шаблон:Yes Шаблон:Yes
mouseover onmouseover Fires when the pointing device is moved onto an element Шаблон:Yes Шаблон:Yes
mousemove[7] onmousemove Fires when the pointing device is moved while it is over an element Шаблон:Yes Шаблон:Yes
mouseout onmouseout Fires when the pointing device is moved away from an element Шаблон:Yes Шаблон:Yes
dragstart ondragstart Fired on an element when a drag is started. Шаблон:Yes Шаблон:Yes
drag ondrag This event is fired at the source of the drag, that is, the element where dragstart was fired, during the drag operation. Шаблон:Yes Шаблон:Yes
dragenter ondragenter Fired when the mouse is first moved over an element while a drag is occurring. Шаблон:Yes Шаблон:Yes
dragleave ondragleave This event is fired when the mouse leaves an element while a drag is occurring. Шаблон:Yes Шаблон:No
dragover ondragover This event is fired as the mouse is moved over an element when a drag is occurring. Шаблон:Yes Шаблон:Yes
drop ondrop The drop event is fired on the element where the drop occurs at the end of the drag operation. Шаблон:Yes Шаблон:Yes
dragend ondragend The source of the drag will receive a dragend event when the drag operation is complete, whether it was successful or not. Шаблон:Yes Шаблон:No
Keyboard keydown onkeydown Fires before keypress, when a key on the keyboard is pressed. Шаблон:Yes Шаблон:Yes
keypress onkeypress Fires after keydown, when a key on the keyboard is pressed. Шаблон:Yes Шаблон:Yes
keyup onkeyup Fires when a key on the keyboard is released Шаблон:Yes Шаблон:Yes
HTML frame/object load onload Fires when the user agent finishes loading all content within a document, including window, frames, objects and images

For elements, it fires when the target element and all of its content has finished loading

Шаблон:No Шаблон:No
unload onunload Fires when the user agent removes all content from a window or frame

For elements, it fires when the target element or any of its content has been removed

Шаблон:No Шаблон:No
abort onabort Fires when an object/image is stopped from loading before completely loaded Шаблон:Yes Шаблон:No
error onerror Fires when an object/image/frame cannot be loaded properly Шаблон:Yes Шаблон:No
resize onresize Fires when a document view is resized Шаблон:Yes Шаблон:No
scroll onscroll Fires when an element or document view is scrolled Шаблон:No, except that a scroll event on document must bubble to the window[8] Шаблон:No
HTML form select onselect Fires when a user selects some text in a text field, including input and textarea Шаблон:Yes Шаблон:No
change onchange Fires when a control loses the input focus and its value has been modified since gaining focus Шаблон:Yes Шаблон:No
submit onsubmit Fires when a form is submitted Шаблон:Yes Шаблон:Yes
reset onreset Fires when a form is reset Шаблон:Yes Шаблон:No
focus onfocus Fires when an element receives focus either via the pointing device or by tab navigation Шаблон:No Шаблон:No
blur onblur Fires when an element loses focus either via the pointing device or by tabbing navigation Шаблон:No Шаблон:No
User interface focusin Шаблон:CNone Similar to HTML focus event, but can be applied to any focusable element Шаблон:Yes Шаблон:No
focusout Шаблон:CNone Similar to HTML blur event, but can be applied to any focusable element Шаблон:Yes Шаблон:No
DOMActivate Шаблон:CNone Similar to XUL command event. Fires when an element is activated, for instance, through a mouse click or a keypress. Шаблон:Yes Шаблон:Yes
Mutation DOMSubtreeModified Шаблон:CNone Fires when the subtree is modified Шаблон:Yes Шаблон:No
DOMNodeInserted Шаблон:CNone Fires when a node has been added as a child of another node Шаблон:Yes Шаблон:No
DOMNodeRemoved Шаблон:CNone Fires when a node has been removed from a DOM-tree Шаблон:Yes Шаблон:No
DOMNodeRemovedFromDocument Шаблон:CNone Fires when a node is being removed from a document Шаблон:No Шаблон:No
DOMNodeInsertedIntoDocument Шаблон:CNone Fires when a node is being inserted into a document Шаблон:No Шаблон:No
DOMAttrModified Шаблон:CNone Fires when an attribute has been modified Шаблон:Yes Шаблон:No
DOMCharacterDataModified Шаблон:CNone Fires when the character data has been modified Шаблон:Yes Шаблон:No
Progress loadstart Шаблон:CNone Progress has begun. Шаблон:No Шаблон:No
progress Шаблон:CNone In progress. After loadstart has been dispatched. Шаблон:No Шаблон:No
error Шаблон:CNone Progression failed. After the last progress has been dispatched, or after loadstart has been dispatched if progress has not been dispatched. Шаблон:No Шаблон:No
abort Шаблон:CNone Progression is terminated. After the last progress has been dispatched, or after loadstart has been dispatched if progress has not been dispatched. Шаблон:No Шаблон:No
load Шаблон:CNone Progression is successful. After the last progress has been dispatched, or after loadstart has been dispatched if progress has not been dispatched. Шаблон:No Шаблон:No
loadend Шаблон:CNone Progress has stopped. After one of error, abort, or load has been dispatched. Шаблон:No Шаблон:No

Note that the events whose names start with "DOM" are currently not well supported, and for this and other performance reasons are deprecated by the W3C in DOM Level 3. Mozilla and Opera support DOMAttrModified, DOMNodeInserted, DOMNodeRemoved and DOMCharacterDataModified. Chrome and Safari support these events, except for DOMAttrModified.

Touch events

Web browsers running on touch-enabled devices, such as Apple's iOS and Google's Android, generate additional events.[9]Шаблон:Rp

Category Type Attribute Description Bubbles Cancelable
Touch touchstart Fires when a finger is placed on the touch surface/screen. Шаблон:Yes Шаблон:Yes
touchend Fires when a finger is removed from the touch surface/screen. Шаблон:Yes Шаблон:Yes
touchmove Fires when a finger already placed on the screen is moved across the screen. Шаблон:Yes Шаблон:Yes
touchenter Fires when a touch point moves onto the interactive area defined by a DOM element. Шаблон:Yes Шаблон:Yes
touchleave Fires when a touch point moves off the interactive area defined by a DOM element. Шаблон:Yes Шаблон:Yes
touchcancel A user agent must dispatch this event type to indicate when a TouchPoint has been disrupted in an implementation-specific manner, such as by moving outside the bounds of the UA window. A user agent may also dispatch this event type when the user places more touch points (The coordinate point at which a pointer (e.g. finger or stylus) intersects the target surface of an interface) on the touch surface than the device or implementation is configured to store, in which case the earliest TouchPoint object in the TouchList should be removed.[9]Шаблон:Rp Шаблон:Yes Шаблон:No

In the W3C draft recommendation, a TouchEvent delivers a TouchList of Touch locations, the modifier keys that were active, a TouchList of Touch locations within the targeted DOM element, and a TouchList of Touch locations that have changed since the previous TouchEvent.[9]

Apple didn't join this working group, and delayed W3C recommendation of its Touch Events Specification by disclosing patents late in the recommendation process.[10]

Pointer events

Web browsers on devices with various types of input devices including mouse, touch panel, and pen may generate integrated input events. Users can see what type of input device is pressed, what button is pressed on that device, and how strongly the button is pressed when it comes to a stylus pen. As of October 2013, this event is only supported by Internet Explorer 10 and 11.[11]

Category Type Attribute Description Bubbles Cancelable
Pointer pointerdown onpointerdown Fires when the pointing device button is activated, or pressed over an element. Шаблон:Yes Шаблон:Yes
pointerup onpointerup Fires when the pointing device button is released over an element Шаблон:Yes Шаблон:Yes
pointercancel onpointercancel Fires when a pointing device is unlikely to continue to produce event because, for example, the device is used for panning/zooming after a pointerdown event. Шаблон:Yes Шаблон:Yes
pointermove onpointermove Fires when the pointing device is moved while it is over an element Шаблон:Yes Шаблон:Yes
pointerover onpointerover Fires when the pointing device is moved onto an element Шаблон:Yes Шаблон:Yes
pointerout onpointerout Fires when the pointing device is moved away from an element. Also fires after pointerup by pointing device without hovering, or after Шаблон:Yes Шаблон:Yes
pointerenter onpointerenter Fires when the pointing device is moved onto an element, or when the button of the pointing device which does not support hovering is pressed on one of its descendant elements. Шаблон:No Шаблон:Yes
pointerleave onpointerleave Fires when the pointing device is moved away from an element, or when the button of the pointing device which does not support hovering is released over its descendant elements. Шаблон:No Шаблон:Yes
gotpointercapture ongotpointercapture Fires when the pointer is captured by setPointerCapture method. Шаблон:Yes Шаблон:No
lostpointercapture onlostpointercapture Fires when the pointer is released by releasePointerCapture method. Шаблон:Yes Шаблон:No

Indie UI events

Not yet really implemented, the Indie UI working groups want to help web application developers to be able to support standard user interaction events without having to handle different platform specific technical events that could match with it.[12]

Scripting usable interfaces can be difficult, especially when one considers that user interface design patterns differ across software platforms, hardware, and locales, and that those interactions can be further customized based on personal preference. Individuals are accustomed to the way the interface works on their own system, and their preferred interface frequently differs from that of the web application author's preferred interface.

For example, web application authors, wishing to intercept a user's intent to undo the last action, need to "listen" for all the following events:

  • Control+Z on Windows and Linux.
  • Command+Z on Mac OS X.
  • Shake events on some mobile devices.

It would be simpler to listen for a single, normalized request to "undo" the previous action.

Category Type Description Bubbles Cancelable
Request undorequest Indicates the user desires to "undo" the previous action. (May be superseded by the UndoManager interface.) Шаблон:Yes Шаблон:Yes
redorequest Indicates the user desires to "redo" the previously "undone" action. (May be superseded by the UndoManager interface.) Шаблон:Yes Шаблон:No
expandrequest Indicates the user desires to reveal information in a collapsed section (e.g. a disclosure widget) or branch node in a hierarchy (e.g., a tree view). Шаблон:Yes Шаблон:Yes
collapserequest Indicates the user desires to hide or collapse information in an expanded section (e.g. a disclosure widget) or branch node in a hierarchy (e.g., a tree view). Шаблон:Yes Шаблон:Yes
dismissrequest Indicates the user desires "dismiss" the current view (e.g. canceling a dialog, or closing a popup menu). Шаблон:Yes Шаблон:Yes
deleterequest Indicates the user wants to initiate a "delete" action on the marked element or current view. Шаблон:Yes Шаблон:Yes
Focus Request directionalfocusrequest Initiated when the user agent sends a "direction focus" request to the web application. Web authors should not use or register for directionalfocusrequest events when standard browser focus and blur events are sufficient. Using these events unnecessarily could result in reduced performance or negative user experience. Шаблон:Yes Шаблон:Yes
linearfocusrequest Initiated when the user agent sends a "linear focus" request to the web application. Web authors should not use or register for linearfocusrequest events when standard browser focus and blur events are sufficient. This event type is only necessary on specialized control types such as data grids where the logical next element may not be focusable or even in the DOM until requested. Using these events unnecessarily could result in reduced performance or negative user experience. Шаблон:Yes Шаблон:Yes
palettefocusrequest Initiated when the user agent sends a "palette focus" request to the web application. Web app authors receiving this event should move focus to the first palette in the web application, or cycle focus between all available palettes. Note: palettes are sometimes referred to as non-modal dialogs or inspector windows. Шаблон:Yes Шаблон:Yes
toolbarfocusrequest Initiated when the user agent sends a "toolbar focus" request to the web application. Web app authors receiving this event should move focus to the main toolbar in the web application, or cycle focus between all available toolbars. Шаблон:Yes Шаблон:Yes
Manipulation Request moverequest Initiated when the user agent sends a move request to the web application with accompanying x/y delta values. This is used, for example, when moving an object to a new location on a layout canvas. Шаблон:Yes Шаблон:Yes
panrequest Initiated when the user agent sends a pan request to the web application with accompanying x/y delta values. This is used, for example, when changing the center point while panning a map or another custom image viewer. Шаблон:Yes Шаблон:Yes
rotationrequest Initiated when the user agent sends a rotation request to the web application with accompanying origin x/y values and a rotation value in degrees. Шаблон:Yes Шаблон:Yes
zoomrequest Initiated when the user agent sends a zoom request to the web application with accompanying origin x/y values and the zoom scale factor. Шаблон:Yes Шаблон:Yes
Scroll Request scrollrequest Initiated when the user agent sends a scroll request to the web application with accompanying x/y delta values or one of the other defined scrollType values. Authors should only use this event and uiaction with custom scroll views. Шаблон:Yes Шаблон:Yes
ValueChange Request valuechangerequest Initiated when the user agent sends a value change request to the web application. Used on custom range controls like sliders, carousels, etc. Шаблон:Yes Шаблон:Yes

Internet Explorer-specific events

In addition to the common (W3C) events, two major types of events are added by Internet Explorer. Some of the events have been implemented as de facto standards by other browsers.

Category Type Attribute Description Bubbles Cancelable
Clipboard cut oncut Fires after a selection is cut to the clipboard. Шаблон:Yes Шаблон:Yes
copy oncopy Fires after a selection is copied to the clipboard. Шаблон:Yes Шаблон:Yes
paste onpaste Fires after a selection is pasted from the clipboard. Шаблон:Yes Шаблон:Yes
beforecut onbeforecut Fires before a selection is cut to the clipboard. Шаблон:Yes Шаблон:Yes
beforecopy onbeforecopy Fires before a selection is copied to the clipboard. Шаблон:Yes Шаблон:Yes
beforepaste onbeforepaste Fires before a selection is pasted from the clipboard. Шаблон:Yes Шаблон:Yes
Data binding afterupdate onafterupdate Fires immediately after a databound object has been updated. Шаблон:Yes Шаблон:No
beforeupdate onbeforeupdate Fires before a data source is updated. Шаблон:Yes Шаблон:Yes
cellchange oncellchange Fires when a data source has changed. Шаблон:Yes Шаблон:No
dataavailable ondataavailable Fires when new data from a data source become available. Шаблон:Yes Шаблон:No
datasetchanged ondatasetchanged Fires when content at a data source has changed. Шаблон:Yes Шаблон:No
datasetcomplete ondatasetcomplete Fires when transfer of data from the data source has completed. Шаблон:Yes Шаблон:No
errorupdate onerrorupdate Fires if an error occurs while updating a data field. Шаблон:Yes Шаблон:No
rowenter onrowenter Fires when a new row of data from the data source is available. Шаблон:Yes Шаблон:No
rowexit onrowexit Fires when a row of data from the data source has just finished. Шаблон:No Шаблон:Yes
rowsdelete onrowsdelete Fires when a row of data from the data source is deleted. Шаблон:Yes Шаблон:No
rowinserted onrowinserted Fires when a row of data from the data source is inserted. Шаблон:Yes Шаблон:No
Mouse contextmenu oncontextmenu Fires when the context menu is shown. Шаблон:Yes Шаблон:Yes
drag ondrag Fires when during a mouse drag (on the moving Element). Шаблон:Yes Шаблон:Yes
dragstart ondragstart Fires when a mouse drag begins (on the moving Element). Шаблон:Yes Шаблон:Yes
dragenter ondragenter Fires when something is dragged onto an area (on the target Element). Шаблон:Yes Шаблон:Yes
dragover ondragover Fires when a drag is held over an area (on the target Element). Шаблон:Yes Шаблон:Yes
dragleave ondragleave Fires when something is dragged out of an area (on the target Element). Шаблон:Yes Шаблон:Yes
dragend ondragend Fires when a mouse drag ends (on the moving Element). Шаблон:Yes Шаблон:Yes
drop ondrop Fires when a mouse button is released over a valid target during a drag (on the target Element). Шаблон:Yes Шаблон:Yes
selectstart onselectstart Fires when the user starts to select text. Шаблон:Yes Шаблон:Yes
Keyboard help onhelp Fires when the user initiates help. Шаблон:Yes Шаблон:Yes
HTML frame/object beforeunload onbeforeunload Fires before a document is unloaded. Шаблон:No Шаблон:Yes
stop onstop Fires when the user stops loading the object. (unlike abort, stop event can be attached to document) Шаблон:No Шаблон:No
HTML form beforeeditfocus onbeforeeditfocus Fires before an element gains focus for editing. Шаблон:Yes Шаблон:Yes
Marquee start onstart Fires when a marquee begins a new loop. Шаблон:No Шаблон:No
finish onfinish Fires when marquee looping is complete. Шаблон:No Шаблон:Yes
bounce onbounce Fires when a scrolling marquee bounces back in the other direction. Шаблон:No Шаблон:Yes
Miscellaneous beforeprint onbeforeprint Fires before a document is printed Шаблон:No Шаблон:No
afterprint onafterprint Fires immediately after the document prints. Шаблон:No Шаблон:No
propertychange onpropertychange Fires when the property of an object is changed. Шаблон:No Шаблон:No
filterchange onfilterchange Fires when a filter changes properties or finishes a transition. Шаблон:No Шаблон:No
readystatechange onreadystatechange Fires when the readyState property of an element changes. Шаблон:No Шаблон:No
losecapture onlosecapture Fires when the releaseCapture method is invoked. Шаблон:No Шаблон:No

Note that Mozilla, Safari and Opera also support the readystatechange event for the XMLHttpRequest object. Mozilla also supports the beforeunload event using the traditional event registration method (DOM Level 0). Mozilla and Safari also support contextmenu, but Internet Explorer for Mac does not.

Note that Firefox 6 and later support the beforeprint and afterprint events.

XUL events

In addition to the common (W3C) events, Mozilla defined a set of events that work only with XUL elements.Шаблон:Citation needed

Category Type Attribute Description Bubbles Cancelable
Mouse DOMMouseScroll DOMMouseScroll Fires when the mouse wheel is moved, causing the content to scroll. Шаблон:Yes Шаблон:Yes
dragdrop ondragdrop Fires when the user releases the mouse button to drop an object being dragged. Шаблон:No Шаблон:No
dragenter ondragenter Fires when the mouse pointer first moves over an element during a drag. It is similar to the mouseover event but occurs while dragging. Шаблон:No Шаблон:No
dragexit ondragexit Fires when the mouse pointer moves away from an element during a drag. It is also called after a drop on an element. It is similar to the mouseout event but occurs during a drag. Шаблон:No Шаблон:No
draggesture ondraggesture Fires when the user starts dragging the element, usually by holding down the mouse button and moving the mouse. Шаблон:No Шаблон:No
dragover ondragover Related to the mousemove event, this event is fired while something is being dragged over an element. Шаблон:No Шаблон:No
Input CheckboxStateChange Fires when a checkbox is checked or unchecked, either by the user or a script. Шаблон:No Шаблон:No
RadioStateChange Fires when a radio button is selected, either by the user or a script. Шаблон:No Шаблон:No
close onclose Fires when a request has been made to close the window. Шаблон:No Шаблон:Yes
command oncommand Similar to W3C DOMActivate event. Fires when an element is activated, for instance, through a mouse click or a keypress. Шаблон:No Шаблон:No
input oninput Fires when a user enters text in a textbox. Шаблон:Yes Шаблон:No
User interface DOMMenuItemActive DOMMenuItemActive Fires when a menu or menuitem is hovered over, or highlighted. Шаблон:Yes Шаблон:No
DOMMenuItemInactive DOMMenuItemInactive Fires when a menu or menuitem is no longer being hovered over, or highlighted. Шаблон:Yes Шаблон:No
contextmenu oncontextmenu Fires when the user requests to open the context menu for the element. The action to do this varies by platform, but it will typically be a right click. Шаблон:No Шаблон:Yes
overflow onoverflow Fires a box or other layout element when there is not enough space to display it at full size. Шаблон:No Шаблон:No
overflowchanged onoverflowchanged Fires when the overflow state changes. Шаблон:No Шаблон:No
underflow onunderflow Fires to an element when there becomes enough space to display it at full size. Шаблон:No Шаблон:No
popuphidden onpopuphidden Fires to a popup after it has been hidden. Шаблон:No Шаблон:No
popuphiding onpopuphiding Fires to a popup when it is about to be hidden. Шаблон:No Шаблон:No
popupshowing onpopupshowing Fires to a popup just before it is popped open. Шаблон:No Шаблон:Yes
popupshown onpopupshown Fires to a popup after it has been opened, much like the onload event is sent to a window when it is opened. Шаблон:No Шаблон:No
Command broadcast onbroadcast Placed on an observer. The broadcast event is sent when the attributes of the broadcaster being listened to are changed. Шаблон:No Шаблон:No
commandupdate oncommandupdate Fires when a command update occurs. Шаблон:No Шаблон:No

Other events

For Mozilla and Opera 9, there are also undocumented events known as DOMContentLoaded and DOMFrameContentLoaded which fire when the DOM content is loaded. These are different from "load" as they fire before the loading of related files (e.g., images). However, DOMContentLoaded has been added to the HTML 5 specification.[13] The DOMContentLoaded event was also implemented in the Webkit rendering engine build 500+.[14][15] This correlates to all versions of Google Chrome and Safari 3.1+. DOMContentLoaded is also implemented in Internet Explorer 9.[16]

Opera 9 also supports the Web Forms 2.0 events DOMControlValueChanged, invalid, forminput and formchange.

Event flow

Consider the situation when two event targets participate in a tree. Both have event listeners registered on the same event type, say "click". When the user clicks on the inner element, there are two possible ways to handle it:

  • Trigger the elements from outer to inner (event capturing). This model is implemented in Netscape Navigator.
  • Trigger the elements from inner to outer (event bubbling). This model is implemented in Internet Explorer and other browsers.[17]

W3C takes a middle position in this struggle.[18]Шаблон:Rp

According to the W3C, events go through three phases when an event target participates in a tree:

  1. The capture phase: the event travels down from the root event target to the target of an event
  2. The target phase: the event travels through the event target
  3. The bubble phase (optional): the event travels back up from the target of an event to the root event target. The bubble phase will only occur for events that bubble (where event.bubbles == true)

You can find a visualization of this event flow at https://domevents.dev

Stopping events

While an event is travelling through event listeners, the event can be stopped with event.stopPropagation() or event.stopImmediatePropagation()

  • event.stopPropagation(): the event is stopped after all event listeners attached to the current event target in the current event phase are finished
  • event.stopImmediatePropagation(): the event is stopped immediately and no further event listeners are executed

When an event is stopped it will no longer travel along the event path. Stopping an event does not cancel an event.

Legacy mechanisms to stop an event

  • Set the event.cancelBubble to true (Internet Explorer)
  • Set the event.returnValue property to false

Canceling events

A cancelable event can be canceled by calling event.preventDefault(). Canceling an event will opt out of the default browser behaviour for that event. When an event is canceled, the event.defaultPrevented property will be set to true. Canceling an event will not stop the event from traveling along the event path.

Event object

The Event object provides a lot of information about a particular event, including information about target element, key pressed, mouse button pressed, mouse position, etc. Unfortunately, there are very serious browser incompatibilities in this area. Hence only the W3C Event object is discussed in this article.

Event properties
Name Type Description
type DOMString The name of the event (case-insensitive in DOM level 2 but case-sensitive in DOM level 3 [19]).
target EventTarget Used to indicate the EventTarget to which the event was originally dispatched.
currentTarget EventTarget Used to indicate the EventTarget whose EventListeners are currently being processed.
eventPhase unsigned short Used to indicate which phase of event flow is currently being evaluated.
bubbles boolean Used to indicate whether or not an event is a bubbling event.
cancelable boolean Used to indicate whether or not an event can have its default action prevented.
timeStamp DOMTimeStamp Used to specify the time (in milliseconds relative to the epoch) at which the event was created.
Event methods
Name Argument type Argument name Description
stopPropagation To prevent further propagation of an event during event flow.
preventDefault To cancel the event if it is cancelable, meaning that any default action normally taken by the implementation as a result of the event will not occur.
initEvent DOMString eventTypeArg Specifies the event type.
boolean canBubbleArg Specifies whether or not the event can bubble.
boolean cancelableArg Specifies whether or not the event's default action can be prevented.

Event handling models

DOM Level 0

This event handling model was introduced by Netscape Navigator, and remains the most cross-browser model Шаблон:As of.Шаблон:Citation needed There are two model types: the inline model and the traditional model.

Inline model

In the inline model,[20] event handlers are added as attributes of elements. In the example below, an alert dialog box with the message "Hey Joe" appears after the hyperlink is clicked. The default click action is cancelled by returning false in the event handler. 

<!doctype html>
<html lang="en">
<head>
	<meta charset="utf-8">
	<title>Inline Event Handling</title>
</head>
<body>

	<h1>Inline Event Handling</h1>

	<p>Hey <a href="http://www.example.com" onclick="triggerAlert('Joe'); return false;">Joe</a>!</p>

	<script>
		function triggerAlert(name) {
			window.alert("Hey " + name);
		}
	</script>
</body>
</html>

One common misconceptionШаблон:Citation needed with the inline model is the belief that it allows the registration of event handlers with custom arguments, e.g. name in the triggerAlert function. While it may seem like that is the case in the example above, what is really happening is that the JavaScript engine of the browser creates an anonymous function containing the statements in the onclick attribute. The onclick handler of the element would be bound to the following anonymous function: 

function () {
	triggerAlert('Joe');
	return false;
}

This limitation of the JavaScript event model is usually overcome by assigning attributes to the function object of the event handler or by using closures.

Traditional model

In the traditional model,[21] event handlers can be added or removed by scripts. Like the inline model, each event can only have one event handler registered. The event is added by assigning the handler name to the event property of the element object. To remove an event handler, simply set the property to null: 

<!doctype html>
<html lang="en">
<head>
	<meta charset="utf-8">
	<title>Traditional Event Handling</title>
</head>

<body>
	<h1>Traditional Event Handling</h1>
	
	<p>Hey Joe!</p>

	<script>
		var triggerAlert = function () {
			window.alert("Hey Joe");
		};
		
		// Assign an event handler
		document.onclick = triggerAlert;
		
		// Assign another event handler
		window.onload = triggerAlert;
		
		// Remove the event handler that was just assigned
		window.onload = null;
	</script>
</body>
</html>

To add parameters: 

var name = 'Joe';
document.onclick = (function (name) {
	return function () {
		alert('Hey ' + name + '!');
	};
}(name));

Inner functions preserve their scope.

DOM Level 2

The W3C designed a more flexible event handling model in DOM Level 2.[18]

Name Description Argument type Argument name
addEventListener Allows the registration of event listeners on the event target. DOMString type
EventListener listener
boolean useCapture
removeEventListener Allows the removal of event listeners from the event target. DOMString type
EventListener listener
boolean useCapture
dispatchEvent Allows sending the event to the subscribed event listeners. Event evt

Some useful things to know :

  • To prevent an event from bubbling, developers must call the stopPropagation() method of the event object.
  • To prevent the default action of the event to be called, developers must call the preventDefault() method of the event object.

The main difference from the traditional model is that multiple event handlers can be registered for the same event. The useCapture option can also be used to specify that the handler should be called in the capture phase instead of the bubbling phase. This model is supported by Mozilla, Opera, Safari, Chrome and Konqueror.

A rewrite of the example used in the traditional model

<!doctype html>
<html lang="en">
<head>
     <meta charset="utf-8">
     <title>DOM Level 2</title>
</head>

<body>
     <h1>DOM Level 2</h1>
     
     <p>Hey Joe!</p>
     
     
     <script>
          var heyJoe = function () {
               window.alert("Hey Joe!");
          }
          
          // Add an event handler
          document.addEventListener( "click", heyJoe, true );  // capture phase
          
          // Add another event handler
          window.addEventListener( "load", heyJoe, false );  // bubbling phase
          
          // Remove the event handler just added
          window.removeEventListener( "load", heyJoe, false );
     </script>

</body>
</html>

Internet Explorer-specific model

Microsoft Internet Explorer prior to version 8 does not follow the W3C model, as its own model was created prior to the ratification of the W3C standard. Internet Explorer 9 follows DOM level 3 events,[22] and Internet Explorer 11 deletes its support for Microsoft-specific model.[23]

Name Description Argument type Argument name
attachEvent Similar to W3C's addEventListener method. String sEvent
Pointer fpNotify
detachEvent Similar to W3C's removeEventListener method. String sEvent
Pointer fpNotify
fireEvent Similar to W3C's dispatchEvent method. String sEvent
Event oEventObject

Some useful things to know :

  • To prevent an event bubbling, developers must set the event's cancelBubble property.
  • To prevent the default action of the event to be called, developers must set the event's returnValue property.
  • The this keyword refers to the global window object.

Again, this model differs from the traditional model in that multiple event handlers can be registered for the same event. However the useCapture option can not be used to specify that the handler should be called in the capture phase. This model is supported by Microsoft Internet Explorer and Trident based browsers (e.g. Maxthon, Avant Browser).

A rewrite of the example used in the old Internet Explorer-specific model

<!doctype html>
<html lang="en">
<head>
     <meta charset="utf-8">
     <title>Internet Explorer-specific model</title>
</head>
<body>
     <h1>Internet Explorer-specific model</h1>

     <p>Hey Joe!</p>

     <script>
          var heyJoe = function () {
               window.alert("Hey Joe!");
          }
          
          // Add an event handler
          document.attachEvent("onclick", heyJoe);
          
          // Add another event handler
          window.attachEvent("onload", heyJoe);
          
          // Remove the event handler just added
          window.detachEvent("onload", heyJoe);
     </script>

</body>
</html>

References

Шаблон:Reflist

Further reading

External links

Шаблон:Web interfaces

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Разное

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  18. ↑ 18,0 18,1 Шаблон:Cite web
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  20. ↑ Шаблон:Cite web
  21. ↑ Шаблон:Cite web
  22. ↑ Шаблон:Cite web
  23. ↑ Шаблон:Cite web
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