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Window Events

The Window object supports many events. Unfortunately, many of these are proprietary. The safe cross-browser window events include onblur, onerror, onfocus, onload, onunload, and onresize and are detailed in Table 12-2.

Table 12-2: Common Window Events

Event

Description

onblur

Fires when the window loses focus.

onerror

Rudimentary error handling event fired when a JavaScript error occurs.

onfocus

Fires when the window gains focus.

onload

Fires when the document is completely loaded into the window. Warning: Timing of this event is not always exact.

onresize

Event triggered as user resizes the window.

onunload

Triggered when the document is unloaded, such as following an outside link or closing the window.

Adding Window events handlers can be set through HTML event attributes on the <<body>> element like so,

<<body onload="alert('entering window');" onunload="alert('leaving window')">>

or by registering events through the Window object:

function sayHi() { alert('hi'); }
function sayBye() { alert('bye'); }
window.onload = sayHi;
window.onunload = sayBye;

Internet Explorer and Netscape add numerous events to the Window object. A few of the more useful ones are detailed in Table 12-3. A general discussion of Window events can be found in Chapter 11 with a complete listing in Appendix B.

Table 12-3: Useful Extended Window Events

Event

Description

onafterprint

Event triggered after the window is printed.

onbeforeprint

Fires just before the window is printed or print previewed.

onbeforeunload

The event is triggered just before the window unloads. Should happen before the onunload event.

ondragdrop

Is triggered when a document is dragged onto a window. (Netscape only.)

onhelp

Fires when the Help key, generally F1, is clicked.

onresizeend

Fires when the resize process ends—usually the user has stopped dragging the corner of a window.

onresizestart

Fires when the resize process begins—usually the user has started dragging the corner of a window.

onscroll

Fires when the window is scrolled in either direction.


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