event | NN 4 IE 4 DOM n/a
While the event object contains information about a user- or system-generated event in Navigator and Internet Explorer, the event mechanisms for the two browser families are very different, as described in . With only a few exceptions, the event object properties for the two browsers are mutually exclusive. Observe the browser compatibility listings for each of the following properties carefully.
Object Model Reference
NN | eventObj
IE | window.event

altKey | NN n/a IE 4 DOM n/a
| Read-only
Reveals the state of the Alt key at the time the event fired.
Example
    if (event.altKey) {
        handle case of Alt key down
    }
Value Boolean value: true | false.
Default | false

button | NN n/a IE 4 DOM n/a
| Read-only
Which mouse button was pressed to trigger the mouse event. Although theoretically you should be able to detect the right button, Internet Explorer 4 does not fire mouse events with that button, since context menus always appear in the browser.
Example
    if (event.button == 1) {
        handle event for left button
    }
Value Any of the following allowed integers: 0 (no button) | 1 (left button) | 2 (right button) | 4 (middle button of three-button mouse).
Default | 0

cancelBubble | NN n/a IE 4 DOM n/a
| Read/Write
Specifies whether the event should propagate (bubble) up the element container hierarchy. You usually only need to set this property to true to override the default behavior and prevent the event from going any further.
Example
    window.event.cancelBubble = true
Value Boolean: true | false.
Default | false

clientX, clientY | NN n/a IE 4 DOM n/a
| Read-only
The horizontal (x) and vertical (y) coordinate of the mouse at the moment the current event fired. These coordinates are relative to the viewable document area of the browser window or frame.
Example
    if ((event.clientX >= 10 || event.clientX <= 20) &&
    (event.clientY >= 50 || event.clientY <= 100)) {
        process code for click in hot zone bounded by 10,50 and 20,100
    }
Value Integer of pixel values.
Default | None.

ctrlKey | NN n/a IE 4 DOM n/a
| Read-only
Whether the Control key was pressed at the instant the event fired. See for testing for this key in cross-browser event handling code.
Example
    if (event.ctrlKey) {
        process for Control key being down
    }
Value Boolean value: true | false.
Default | false

data | NN 4 IE n/a DOM n/a
| Read-only
Accessory data associated with the event. As of Navigator 4, the only event for which the data property has information is the dragdrop event, in which case the data property returns the URL of the item being dropped onto the window or frame.
Example
    var srcDoc = evtObj.data
Value String.
Default | None.

fromElement | NN n/a IE 4 DOM n/a
| Read-only
Returns a reference to the object where the cursor had been just prior to the onMouseOver or onMouseOut event.
Example
    if (event.fromElement.id == "lowerLevel") {
        ...
    }
Value Object reference.
Default | None.

keyCode | NN n/a IE 4 DOM n/a
| Read/Write
The Unicode key value for the keyboard key that triggered the event. For onKeyPress events, the value represents the actual character displayed in a text box (e.g., 65 for "A" and 97 for "a"). But for onKeyDown and onKeyUp events, only the uppercase value is returned, regardless of the case of the character that is rendered. If the event is not keyboard driven, the value is zero. While you may change the value of this property, it does not influence the character displayed in the text field. See about capturing keyboard events.
Example
    if (event.keyCode == 65) {
        ...
    }
Value Integer.
Default | None.

layerX, layerY | NN 4 IE n/a DOM n/a
| Read-only
The horizontal (x) and vertical (y) coordinate of the mouse at the moment the current event fired. These coordinates are relative to the containing layer. If no layers or positionable elements have been defined, the default layer of the base document is used as a reference point, thus being equivalent to the pageX and pageY properties.
Example
    if ((evtObj.layerX >= 10 || evtObj.layerX <= 20) &&
    (evtObj.layerY >= 50 || evtObj.layerY <= 100)) {
        process code for click in hot zone bounded by 10,50 and 20,100
    }
Value Integer of pixel values.
Default | None.

modifiers | NN 4 IE n/a DOM n/a
| Read-only
An integer that represents the keyboard modifier key(s) being held down at the time the event fired. You can use the & operator with a series of Event object constants to find out whether a particular modifier key was pressed. See .
Example
    var altKeyPressed = evtObj.modifiers & Event.ALT_MASK
Value Integer.
Default | 0

offsetX, offsetY | NN n/a IE 4 DOM n/a
| Read-only
The left and top coordinates of the mouse pointer relative to the containing element (exclusive of padding, borders, or margins) when the event fired. You can determine the containing element via the offsetParent property. See the section "About client- and offset- Properties" at the beginning of this chapter about offset measurement anomalies in Internet Explorer 4.
Example
    if (event.offsetX <= 20 && event.offsetY <=40) {
        ...
    }
Value Integer pixel count.
Default | None.

pageX, pageY | NN 4 IE n/a DOM n/a
| Read-only
The left and top coordinates of the element's content relative to the top-left corner of the page area when the event fired. The measurements ignore any scrolling of the page.
Example
    if (evtObj.pageX <= 20 && evtObj.pageY <=40) {
        ...
    }
Value Integer pixel count.
Default | None.

reason | NN n/a IE 4 DOM n/a
| Read-only
Returns a code associated with an onDataSetComplete event signifying whether the data transfer was successful or, if incomplete, whether the transfer stopped due to an error or a stoppage by the client or user. This property must be examined in an event handler for the onDataSetComplete event.
Example
    if (event.reason == 2) {
        alert("An error occurred during the most recent update.")
    }
Value One of three possible integer values:
0 | Transfer was successful
1 | Transfer aborted
2 | An error halted the transfer
Default | None.

returnValue | NN n/a IE 4 DOM n/a
| Read/Write
The value to be returned to the event's source element to allow or prohibit the element's default action connected with the event. If you set event.returnValue to false, the element does not carry out its normal operation, such as navigating to a link or submitting the form.
Example
    event.returnValue = "false"
Value Boolean value: true | false.
Default | true

screenX, screenY | NN 4 IE 4 DOM n/a
| Read-only
Horizontal and vertical pixel coordinate points where the cursor was located on the video screen when the event occurred. The top-left corner of the screen is point 0,0. There is no particular coordination with the browser window, unless you have positioned the window and know where the active window area is in relation to the screen.
Example
    // NN
    if (evtObj.screenX < 5 || evtObj.screenY < 5) {
        alert("You\'re too close to the edge!")
    }
    // IE
    if (event.screenX < 5 || event.screenY < 5) {
        alert("You\'re too close to the edge!")
    }
Value Any positive integer or zero.
Default | None.

shiftKey | NN n/a IE 4 DOM n/a
| Read-only
Reveals the state of the Shift key at the time the event fired.
Example
    if (event.shiftKey) {
        handle case of Shift key down
    }
Value Boolean value: true | false.
Default | false

srcElement | NN n/a IE 4 DOM n/a
| Read-only
Reference to the element object that fired the current event. This property is convenient in switch constructions for an event handler function that handles the same event type for a number of different elements.
Example
    switch (event.srcElement.id) {
        case myDIV:
            ...
        ...
    }
Value Object reference.
Default | None.

srcFilter | NN n/a IE 4 DOM n/a
| Read-only
Reference to the filter object that fired the current onFilterChange event. This property is convenient in switch constructions for an event handler function that handles the same event type for a number of different elements.
Example
    switch (event.srcFilter.id) {
        case myDIV:
            ...
        ...
    }
Value Object reference.
Default | None.

target | NN 4 IE n/a DOM n/a
| Read-only
Reference to the element object that is the intended destination of the current event. This property is convenient in switch constructions for an event handler function that handles the same event type for a number of different elements.
Example
    switch (evtObj.target.name) {
        case "myButton":
            ...
        ...
    }
Value Object reference.
Default | None.

toElement | NN n/a IE 4 DOM n/a
| Read-only
Returns a reference to the object to which the cursor has moved that triggered the onMouseOut event.
Example
    if (event.toElement.id == "upperLevel") {
        ...
    }
Value Object reference.
Default | None.

type | NN 4 IE 4 DOM n/a
| Read-only
The type of the current event (without the "on" prefix). Values are all lowercase.
Example
    // NN
    if (evtObj.type ==  "change") {
        ...
    }
    // IE
    if (event.type ==  "change") {
        ...
    }
Value Any event name (without the "on" prefix) as a string.
Default | None.

which | NN 4 IE n/a DOM n/a
| Read-only
Returns a value relevant to the type of event. For mouse events, the property value is an integer indicating which mouse button was used (1 is the left button; 3 is the right button). For keyboard events, the property value is an integer of the keyboard character ASCII code.
Example
    if (evtObj.which == 65) {
        ...
    }
Value Integer.
Default | None.

x, y | NN n/a IE 4 DOM n/a
| Read-only
Returns the horizontal and vertical pixel coordinates of the mouse pointer at the time the event occurred. The coordinate system is either a positioned element or the BODY element. A value of -1 is returned if the pointer was outside of the document area of the browser window.
Example
    if (event.x < 20 && event.y < 30) {
        ...
    }
Value Integer.
Default | None.