# DOM event

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. 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
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.
* 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 (used by XMLHttpRequest and File API).
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 | Yes | Yes |
| Mouse | dblclick | ondblclick | Fires when the pointing device button is double-clicked over an element | Yes | Yes |
| Mouse | mousedown | onmousedown | Fires when the pointing device button is pressed over an element | Yes | Yes |
| Mouse | mouseup | onmouseup | Fires when the pointing device button is released over an element | Yes | Yes |
| Mouse | mouseover | onmouseover | Fires when the pointing device is moved onto an element | Yes | Yes |
| Mouse | mousemove | onmousemove | Fires when the pointing device is moved while it is over an element | Yes | Yes |
| Mouse | mouseout | onmouseout | Fires when the pointing device is moved away from an element | Yes | Yes |
| Mouse | dragstart | ondragstart | Fired on an element when a drag is started. | Yes | Yes |
| Mouse | drag | ondrag | This event is fired at the source of the drag, that is, the element where dragstart was fired, during the drag operation. | Yes | Yes |
| Mouse | dragenter | ondragenter | Fired when the mouse is first moved over an element while a drag is occurring. | Yes | Yes |
| Mouse | dragleave | ondragleave | This event is fired when the mouse leaves an element while a drag is occurring. | Yes | No |
| Mouse | dragover | ondragover | This event is fired as the mouse is moved over an element when a drag is occurring. | Yes | Yes |
| Mouse | drop | ondrop | The drop event is fired on the element where the drop occurs at the end of the drag operation. | Yes | Yes |
| Mouse | dragend | ondragend | The source of the drag will receive a dragend event when the drag operation is complete, whether it was successful or not. | Yes | No |
| Keyboard | keydown | onkeydown | Fires before keypress, when a key on the keyboard is pressed. | Yes | Yes |
| Keyboard | keypress | onkeypress | Fires after keydown, when a key on the keyboard is pressed. | Yes | Yes |
| Keyboard | keyup | onkeyup | Fires when a key on the keyboard is released | Yes | 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 | No | No |
| HTML frame/object | 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 | No | No |
| HTML frame/object | abort | onabort | Fires when an object/image is stopped from loading before completely loaded | Yes | No |
| HTML frame/object | error | onerror | Fires when an object/image/frame cannot be loaded properly | Yes | No |
| HTML frame/object | resize | onresize | Fires when a document view is resized | Yes | No |
| HTML frame/object | scroll | onscroll | Fires when an element or document view is scrolled | No, except that a scroll event on document must bubble to the window | No |
| HTML form | select | onselect | Fires when a user selects some text in a text field, including input and textarea | Yes | No |
| HTML form | change | onchange | Fires when a control loses the input focus and its value has been modified since gaining focus | Yes | No |
| HTML form | submit | onsubmit | Fires when a form is submitted | Yes | Yes |
| HTML form | reset | onreset | Fires when a form is reset | Yes | No |
| HTML form | focus | onfocus | Fires when an element receives focus either via the pointing device or by tab navigation | No | No |
| HTML form | blur | onblur | Fires when an element loses focus either via the pointing device or by tabbing navigation | No | No |
| User interface | focusin | (none) | Similar to HTML focus event, but can be applied to any focusable element | Yes | No |
| User interface | focusout | (none) | Similar to HTML blur event, but can be applied to any focusable element | Yes | No |
| User interface | DOMActivate | (none) | Similar to XUL command event. Fires when an element is activated, for instance, through a mouse click or a keypress. | Yes | Yes |
| Mutation | DOMSubtreeModified | (none) | Fires when the subtree is modified | Yes | No |
| Mutation | DOMNodeInserted | (none) | Fires when a node has been added as a child of another node | Yes | No |
| Mutation | DOMNodeRemoved | (none) | Fires when a node has been removed from a DOM-tree | Yes | No |
| Mutation | DOMNodeRemovedFromDocument | (none) | Fires when a node is being removed from a document | No | No |
| Mutation | DOMNodeInsertedIntoDocument | (none) | Fires when a node is being inserted into a document | No | No |
| Mutation | DOMAttrModified | (none) | Fires when an attribute has been modified | Yes | No |
| Mutation | DOMCharacterDataModified | (none) | Fires when the character data has been modified | Yes | No |
| Progress | loadstart | (none) | Progress has begun. | No | No |
| Progress | progress | (none) | In progress. After loadstart has been dispatched. | No | No |
| Progress | error | (none) | Progression failed. After the last progress has been dispatched, or after loadstart has been dispatched if progress has not been dispatched. | No | No |
| Progress | abort | (none) | Progression is terminated. After the last progress has been dispatched, or after loadstart has been dispatched if progress has not been dispatched. | No | No |
| Progress | load | (none) | Progression is successful. After the last progress has been dispatched, or after loadstart has been dispatched if progress has not been dispatched. | No | No |
| Progress | loadend | (none) | Progress has stopped. After one of error, abort, or load has been dispatched. | No | 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.$^{:§5.3}$
| Category | Type | Description | Bubbles | Cancelable |
| Touch | touchstart | Fires when a finger is placed on the touch surface/screen. | Yes | Yes |
| Touch | touchend | Fires when a finger is removed from the touch surface/screen. | Yes | Yes |
| Touch | touchmove | Fires when a finger already placed on the screen is moved across the screen. | Yes | Yes |
| Touch | touchenter | Fires when a touch point moves onto the interactive area defined by a DOM element. | Yes | Yes |
| Touch | touchleave | Fires when a touch point moves off the interactive area defined by a DOM element. | Yes | Yes |
| Touch | 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.$^{:§5.9}$ | Yes | 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.
Apple didn't join this working group, and delayed W3C recommendation of its Touch Events Specification by disclosing patents late in the recommendation process.

#### 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.
| Category | Type | Attribute | Description | Bubbles | Cancelable |
| Pointer | pointerdown | onpointerdown | Fires when the pointing device button is activated, or pressed over an element. | Yes | Yes |
| Pointer | pointerup | onpointerup | Fires when the pointing device button is released over an element | Yes | Yes |
| Pointer | 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. | Yes | Yes |
| Pointer | pointermove | onpointermove | Fires when the pointing device is moved while it is over an element | Yes | Yes |
| Pointer | pointerover | onpointerover | Fires when the pointing device is moved onto an element | Yes | Yes |
| Pointer | pointerout | onpointerout | Fires when the pointing device is moved away from an element. Also fires after pointerup by pointing device without hovering, or after | Yes | Yes |
| Pointer | 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. | No | Yes |
| Pointer | 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. | No | Yes |
| Pointer | gotpointercapture | ongotpointercapture | Fires when the pointer is captured by setPointerCapture method. | Yes | No |
| Pointer | lostpointercapture | onlostpointercapture | Fires when the pointer is released by releasePointerCapture method. | Yes | 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.
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.) | Yes | Yes |
| Request | redorequest | Indicates the user desires to "redo" the previously "undone" action. (May be superseded by the UndoManager interface.) | Yes | No |
| Request | 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). | Yes | Yes |
| Request | 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). | Yes | Yes |
| Request | dismissrequest | Indicates the user desires "dismiss" the current view (e.g. canceling a dialog, or closing a popup menu). | Yes | Yes |
| Request | deleterequest | Indicates the user wants to initiate a "delete" action on the marked element or current view. | Yes | 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. | Yes | Yes |
| Focus Request | 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. | Yes | Yes |
| Focus Request | 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. | Yes | Yes |
| Focus Request | 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. | Yes | 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. | Yes | Yes |
| Manipulation Request | 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. | Yes | Yes |
| Manipulation Request | 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. | Yes | Yes |
| Manipulation Request | 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. | Yes | 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. | Yes | 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. | Yes | 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.
* Clipboard events.
* Data binding events.
| Category | Type | Attribute | Description | Bubbles | Cancelable |
| Clipboard | cut | oncut | Fires after a selection is cut to the clipboard. | Yes | Yes |
| Clipboard | copy | oncopy | Fires after a selection is copied to the clipboard. | Yes | Yes |
| Clipboard | paste | onpaste | Fires after a selection is pasted from the clipboard. | Yes | Yes |
| Clipboard | beforecut | onbeforecut | Fires before a selection is cut to the clipboard. | Yes | Yes |
| Clipboard | beforecopy | onbeforecopy | Fires before a selection is copied to the clipboard. | Yes | Yes |
| Clipboard | beforepaste | onbeforepaste | Fires before a selection is pasted from the clipboard. | Yes | Yes |
| Data binding | afterupdate | onafterupdate | Fires immediately after a databound object has been updated. | Yes | No |
| Data binding | beforeupdate | onbeforeupdate | Fires before a data source is updated. | Yes | Yes |
| Data binding | cellchange | oncellchange | Fires when a data source has changed. | Yes | No |
| Data binding | dataavailable | ondataavailable | Fires when new data from a data source become available. | Yes | No |
| Data binding | datasetchanged | ondatasetchanged | Fires when content at a data source has changed. | Yes | No |
| Data binding | datasetcomplete | ondatasetcomplete | Fires when transfer of data from the data source has completed. | Yes | No |
| Data binding | errorupdate | onerrorupdate | Fires if an error occurs while updating a data field. | Yes | No |
| Data binding | rowenter | onrowenter | Fires when a new row of data from the data source is available. | Yes | No |
| Data binding | rowexit | onrowexit | Fires when a row of data from the data source has just finished. | No | Yes |
| Data binding | rowsdelete | onrowsdelete | Fires when a row of data from the data source is deleted. | Yes | No |
| Data binding | rowinserted | onrowinserted | Fires when a row of data from the data source is inserted. | Yes | No |
| Mouse | contextmenu | oncontextmenu | Fires when the context menu is shown. | Yes | Yes |
| Mouse | drag | ondrag | Fires when during a mouse drag (on the moving Element). | Yes | Yes |
| Mouse | dragstart | ondragstart | Fires when a mouse drag begins (on the moving Element). | Yes | Yes |
| Mouse | dragenter | ondragenter | Fires when something is dragged onto an area (on the target Element). | Yes | Yes |
| Mouse | dragover | ondragover | Fires when a drag is held over an area (on the target Element). | Yes | Yes |
| Mouse | dragleave | ondragleave | Fires when something is dragged out of an area (on the target Element). | Yes | Yes |
| Mouse | dragend | ondragend | Fires when a mouse drag ends (on the moving Element). | Yes | Yes |
| Mouse | drop | ondrop | Fires when a mouse button is released over a valid target during a drag (on the target Element). | Yes | Yes |
| Mouse | selectstart | onselectstart | Fires when the user starts to select text. | Yes | Yes |
| Keyboard | help | onhelp | Fires when the user initiates help. | Yes | Yes |
| HTML frame/object | beforeunload | onbeforeunload | Fires before a document is unloaded. | No | Yes |
| HTML frame/object | stop | onstop | Fires when the user stops loading the object. (unlike abort, stop event can be attached to document) | No | No |
| HTML form | beforeeditfocus | onbeforeeditfocus | Fires before an element gains focus for editing. | Yes | Yes |
| Marquee | start | onstart | Fires when a marquee begins a new loop. | No | No |
| Marquee | finish | onfinish | Fires when marquee looping is complete. | No | Yes |
| Marquee | bounce | onbounce | Fires when a scrolling marquee bounces back in the other direction. | No | Yes |
| Miscellaneous | beforeprint | onbeforeprint | Fires before a document is printed | No | No |
| Miscellaneous | afterprint | onafterprint | Fires immediately after the document prints. | No | No |
| Miscellaneous | propertychange | onpropertychange | Fires when the property of an object is changed. | No | No |
| Miscellaneous | filterchange | onfilterchange | Fires when a filter changes properties or finishes a transition. | No | No |
| Miscellaneous | readystatechange | onreadystatechange | Fires when the readyState property of an element changes. | No | No |
| Miscellaneous | losecapture | onlosecapture | Fires when the releaseCapture method is invoked. | No | 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.
| Category | Type | Attribute | Description | Bubbles | Cancelable |
| Mouse | DOMMouseScroll | DOMMouseScroll | Fires when the mouse wheel is moved, causing the content to scroll. | Yes | Yes |
| Mouse | dragdrop | ondragdrop | Fires when the user releases the mouse button to drop an object being dragged. | No | No |
| Mouse | 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. | No | No |
| Mouse | 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. | No | No |
| Mouse | draggesture | ondraggesture | Fires when the user starts dragging the element, usually by holding down the mouse button and moving the mouse. | No | No |
| Mouse | dragover | ondragover | Related to the mousemove event, this event is fired while something is being dragged over an element. | No | No |
| Input | CheckboxStateChange | | Fires when a checkbox is checked or unchecked, either by the user or a script. | No | No |
| Input | RadioStateChange | | Fires when a radio button is selected, either by the user or a script. | No | No |
| Input | close | onclose | Fires when a request has been made to close the window. | No | Yes |
| Input | command | oncommand | Similar to W3C DOMActivate event. Fires when an element is activated, for instance, through a mouse click or a keypress. | No | No |
| Input | input | oninput | Fires when a user enters text in a textbox. | Yes | No |
| User interface | DOMMenuItemActive | DOMMenuItemActive | Fires when a menu or menuitem is hovered over, or highlighted. | Yes | No |
| User interface | DOMMenuItemInactive | DOMMenuItemInactive | Fires when a menu or menuitem is no longer being hovered over, or highlighted. | Yes | No |
| User interface | 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. | No | Yes |
| User interface | overflow | onoverflow | Fires a box or other layout element when there is not enough space to display it at full size. | No | No |
| User interface | overflowchanged | onoverflowchanged | Fires when the overflow state changes. | No | No |
| User interface | underflow | onunderflow | Fires to an element when there becomes enough space to display it at full size. | No | No |
| User interface | popuphidden | onpopuphidden | Fires to a popup after it has been hidden. | No | No |
| User interface | popuphiding | onpopuphiding | Fires to a popup when it is about to be hidden. | No | No |
| User interface | popupshowing | onpopupshowing | Fires to a popup just before it is popped open. | No | Yes |
| User interface | 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. | No | No |
| Command | broadcast | onbroadcast | Placed on an observer. The broadcast event is sent when the attributes of the broadcaster being listened to are changed. | No | No |
| Command | commandupdate | oncommandupdate | Fires when a command update occurs. | No | 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. The DOMContentLoaded event was also implemented in the Webkit rendering engine build 500+. This correlates to all versions of Google Chrome and Safari 3.1+. DOMContentLoaded is also implemented in Internet Explorer 9.
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.
W3C takes a middle position in this struggle.$^{:§1.2}$
According to the W3C, events go through three phases when an event target participates in a tree:
* The capture phase: the event travels down from the root event target to the target of an event
* The target phase: the event travels through the event target
* 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). |
| 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. |
| initEvent | boolean | canBubbleArg | Specifies whether or not the event can bubble. |
| initEvent | 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 as of 2005. There are two model types: the inline model and the traditional model.

#### Inline model

In the inline model, 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.
One common misconception 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:
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, 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:
To add parameters:
Inner functions preserve their scope.

### DOM Level 2

The W3C designed a more flexible event handling model in DOM Level 2.
| Name | Description | Argument type | Argument name |
| addEventListener | Allows the registration of event listeners on the event target. | DOMString | type |
| addEventListener | Allows the registration of event listeners on the event target. | EventListener | listener |
| addEventListener | Allows the registration of event listeners on the event target. | boolean | useCapture |
| removeEventListener | Allows the removal of event listeners from the event target. | DOMString | type |
| removeEventListener | Allows the removal of event listeners from the event target. | EventListener | listener |
| removeEventListener | Allows the removal of event listeners from the event target. | 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
### 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, and Internet Explorer 11 deletes its support for Microsoft-specific model.
| Name | Description | Argument type | Argument name |
| attachEvent | Similar to W3C's addEventListener method. | String | sEvent |
| attachEvent | Similar to W3C's addEventListener method. | Pointer | fpNotify |
| detachEvent | Similar to W3C's removeEventListener method. | String | sEvent |
| detachEvent | Similar to W3C's removeEventListener method. | Pointer | fpNotify |
| fireEvent | Similar to W3C's dispatchEvent method. | String | sEvent |
| fireEvent | Similar to W3C's dispatchEvent method. | 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).