JavaScript Bible, Gold Edition part 39 ppsx

clientInformation NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 In an effort to provide scriptable access to browser-level properties while avoid-ing reference to the Navigator browser bra

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opens a window That window is a valid windowobject, even if the window is blank Therefore, after a user loads your page into the browser, the windowobject part of that document is automatically created for your script to access as it pleases One conceptual trap to avoid is believing that a windowobject’s event handler or custom property assignments outlive the document whose scripts make the assign-ments Except for some obvious physical properties of a window, each new docu-ment that loads into the window starts with a clean slate of window properties and event handlers

Your script’s control over an existing (already open) window’s user interface elements varies widely with the browser and browser version for which your appli-cation is intended Before the version 4 browsers, the only change you can make to

an open window is to the status line at the bottom of the browser window With IE4+ and NN4+, however, you can control such properties as the size, location, and (with signed scripts in Navigator) the presence of “chrome” elements (toolbars and scrollbars, for example) on the fly Many of these properties can be changed beyond specific safe limits only if you cryptographically sign the scripts (see Chapter 46) and/or the user grants permission for your scripts to make those modifications

Window properties are far more flexible on all browsers when your scripts gener-ate a new window (with the window.open()method): You can influence the size, toolbar, or other view options of a window Recent browser versions provide even more options for new windows, including the position of the window and whether the window should even display a title bar Again, if an option can conceivably be used to deceive a user (for example, silently hiding one window that monitors activity in another window), signed scripts and/or user permission are necessary The windowobject is also the level at which a script asks the browser to display any of three styles of dialog boxes (a plain alert dialog box, an OK/Cancel confirma-tion dialog box, or a prompt for user text entry) Although dialog boxes are

extremely helpful for cobbling together debugging tools for your own use (Chapter 45), they can be very disruptive to visitors who navigate through Web sites

Because most JavaScript dialog boxes are modal (that is, you cannot do anything else in the browser — or anything at all on a Macintosh — until you dismiss the dialog box), use them sparingly, if at all Remember that some users may create macros on their computers to visit sites unattended Should such an automated access of your site encounter a modal dialog box, it is trapped on your page until a human intervenes

All dialog boxes generated by JavaScript identify themselves as being generated

by JavaScript (less egregiously so in version 4 browsers and later) This is primarily

a security feature to prevent deceitful scripts from creating system- or application-style dialog boxes that convince visitors to enter private information It should also discourage dialog box usage in Web page design And that’s good, because dialog boxes tend to annoy users

With the exception of the IE-specific modal and modeless dialog boxes (see the

window.showModalDialog()and window.showModeless()methods), JavaScript dialog boxes are not particularly flexible in letting you fill them with text or graphic elements beyond the basics In fact, you can’t even change the text of the dialog box buttons or add a button With DHTML-capable browsers, you can use positioned DIV

or IFRAME elements to simulate dialog box behavior in a cross-browser way

windowObject

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appCore

Components

controllers

prompter

sidebar

NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5

Navigator 6 provides scriptable access to numerous services that are part of the

xpconnect package (“xp” stands for “cross-platform”) These services allow scripts

to work with COM objects and the mozilla.org XUL (XML-based User Interface

Language) facilities — lengthy subjects that extend well beyond the scope of this

book You can begin to explore this subject within the context of Navigator 6 and

scripting at http://www.mozilla.org/scriptable/

clientInformation

In an effort to provide scriptable access to browser-level properties while

avoid-ing reference to the Navigator browser brand, Microsoft provides the

clientInformationproperty Its value is identical to that of the navigator

object — an object name that is also available in IE Use the navigatorobject for

cross-browser applications (See Chapter 28.)

Related Items:navigatorobject

clipboardData

windowObject.clipboardData

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Use the clipboardDataobject (not implemented in IE5/Mac) to transfer data for such actions as cutting, copying, and pasting under script control The object contains data of one or more data types associated with a transfer operation Use this property only when editing processes via the Edit menu (or keyboard equiva-lents) or context menu controlled by script — typically in concert with edit-related event handlers

Working with the clipboardDataobject requires knowing about its three meth-ods shown in Table 16-1 Familiarity with the edit-related event handlers (“before” and “after” versions of cut, copy, and paste) is also helpful (see Chapter 15)

Table 16-1 window.clipboardData Object Methods

Method Returns Description

clearData([format]) Nothing Removes data from the clipboard If no

format parameter is supplied, all data is cleared Data formats can be one or more of the following strings: Text, URL, File, HTML , Image.

getData(format) String Retrieves data of the specified format from

the clipboard The format is one of the following strings: Text, URL, File, HTML, Image The clipboard is not emptied when you get the data, so that the data can be retrieved in several sequential operations.

setData(format, data) Boolean Stores string data in the clipboard The

format is one of the following strings: Text, URL , File, HTML, Image For non-text data formats, the data must be a string that specifies the path or URL to the content Returns true if the transfer to the clipboard

is successful.

You cannot use the clipboardDataobject to transfer data between pages that originate from different domains or arrive via different protocols (httpversus

https)

Example on the CD-ROM

Related Items:event.dataTransferproperty; onBeforeCopy, onBeforeCut,

onBeforePaste, onCopy, onCut, onPasteevent handlers

On the

CD-ROM

windowObject.clipboardData

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When you create a subwindow with the window.open()method, you may need

to access object properties from that subwindow, such as setting the value of a text

field Access to the subwindow is via the windowobject reference that is returned

by the window.open()method, as in the following code fragment:

var newWind = window.open(“someURL.html”,”subWind”)

newWind.document.entryForm.ZIP.value = “00000”

In this example, the newWindvariable is not linked “live” to the window, but is

only a reference to that window If the user should close the window, the newWind

variable still contains the reference to the now missing window Thus, any script

reference to an object in that missing window will likely cause a script error What

you need to know before accessing items in a subwindow is whether the window is

still open

The closedproperty returns trueif the windowobject has been closed either

by script or by the user Any time you have a script statement that can be triggered

after the user has an opportunity to close the window, test for the closedproperty

before executing that statement

As a workaround for Navigator 2, any property of a closed window reference

returns a nullvalue Thus, you can test whether, say, the parentproperty of the

new window is null: If so, the window has already closed Internet Explorer 3, on

the other hand, triggers a scripting error if you attempt to access a property of a

closed window — you have no error-free way to detect whether a window is open or

closed in Internet Explorer 3

Example (with Listing 16-4) on the CD-ROM

Related Items:window.open(), window.close()methods

Components

See appCore

controllers

See appCore

On the

CD-ROM

windowObject.controllers

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pkcs11

The cryptoand pkcs11properties return references to browser objects that are relevant to internal public-key cryptography mechanisms These subjects are beyond the scope of this book, but you can read more about Netscape’s efforts on this front at http://www.mozilla.org/projects/security/

defaultStatus

After a document is loaded into a window or frame, the statusbar’s message field can display a string that is visible any time the mouse pointer is not atop an object that takes precedence over the statusbar (such as a link object or an image map) The window.defaultStatusproperty is normally an empty string, but you can set this property at any time Any setting of this property will be temporarily overrid-den when a user moves the mouse pointer atop a link object (see window.status

property for information about customizing this temporary statusbar message) Probably the most common time to set the window.defaultStatusproperty is when a document loads into a window You can do this as an immediate script statement that executes from the Head or Body portion of the document or as part

of a document’s onLoadevent handler

The defaultStatus property does not work well in Navigator 2 or Internet Explorer 3, and experiences problems in Navigator 3, especially on the Macintosh (where the property doesn’t change even after loading a different document into the window) Many users simply don’t notice the statusbar change during Web surfing, so don’t put mission-critical information in the statusbar

Related Items:window.statusproperty

On the

CD-ROM

Tip

windowObject.defaultStatus

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The dialogArgumentsproperty is available only in a window that is generated

by the IE-specific showModalDialog()or showModelessDialog()methods Those

methods allow a parameter to be passed to the dialog box window, and the

dialogArgumentsproperty lets scripts inside the dialog box window’s scripts to

access that parameter value The value can be in the form of a string, number, or

JavaScript array (convenient for passing multiple values)

Related Items:window.showModalDialog(), window.showModelessDialog()

methods

dialogHeight

dialogWidth

Scripts in a document located inside an IE-specific modal or modeless dialog

box (generated by showModalDialog()or showModelessDialog()) can read or

modify the height and width of the dialog box window via the dialogHeightand

dialogWidthproperties Scripts can access these properties from the main

window only for modeless dialog boxes, which remain visible while the user can

control the main window contents

Values for these properties are strings and include the unit of measure, the

pixel (px)

Related Items:window.dialogLeft, window.dialogTopproperties

On the

CD-ROM

On the

CD-ROM

windowObject.dialogHeight

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dialogTop

Scripts in a document located inside an IE-specific modal or modeless dialog box (generated by showModalDialog()or showModelessDialog()) can read or mod-ify the left and top coordinates of the dialog box window via the dialogLeftand

dialogTopproperties Scripts can access these properties from the main window only for modeless dialog boxes, which remain visible while the user can control the main window contents

Values for these properties are strings and include the unit of measure, the pixel (px) If you attempt to change these values so that any part of the dialog box win-dow would be outside the video monitor, the browser overrides the settings to keep the entire window visible

Related Items:window.dialogHeight, window.dialogTopWidthproperties

directories

locationbar

menubar

personalbar

scrollbars

statusbar

toolbar

Value: Object Read/Write (with signed scripts)

Beyond the rectangle of the content region of a window (where your documents appear), the Netscape browser window displays an amalgam of bars and other

fea-tures known collectively as chrome All browsers can elect to remove these chrome

On the

CD-ROM

windowObject.directories

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items when creating a new window (as part of the third parameter of the

window.open()method), but until signed scripts were available in Navigator 4,

these items could not be turned on and off in the main browser window or any

existing window

Navigator 4 promotes these elements to first-class objects contained by the

windowobject Navigator 6 adds one more feature, called the directories bar — a

frame-like device that can be opened or hidden from the left edge of the browser

window At the same time, however, NN6 no longer permits hiding and showing the

browser window’s scrollbars Figure 16-4 points out where each of the six bars

appears in a fully chromed Navigator 4 window The only element that is not part of

this scheme is the window’s title bar You can create a new window without a title

bar (with a signed script), but you cannot hide and show the title bar on an existing

window

Figure 16-4: Window chrome items

Chrome objects have but one property: visible Reading this Boolean value

(possible without signed scripts) lets you inspect the visitor’s browser window for

the elements currently engaged There is no intermediate setting or property for

the expanded/collapsed state of the toolbar, locationbar, and personalbar in NN4

Changing the visibility of these items on the fly alters the relationship between

the inner and outer dimensions of the browser window If you must carefully size a

window to display content, you should adjust the chrome elements before sizing

the window Before you start changing chrome visibility before the eyes of your

page visitors, weigh the decision carefully Experienced users have fine-tuned the

look of their browser windows to just the way they like them If you mess with that

Menubar

Personalbar Statusbar Locationbar

windowObject.directories

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look, you may anger your visitors Fortunately, changes you make to a chrome ele-ment’s visibility are not stored to the user’s preferences However, the changes you make survive an unloading of the page If you change the settings, be sure you first save the initial settings and restore them with an onUnloadevent handler

The Macintosh menu bar is not part of the browser’s window chrome Therefore, its visibility cannot be adjusted from a script

Related Items:window.open()method

document

I list the documentproperty here primarily for completeness Each window

object contains a single documentobject (although in Navigator 4, a window may also contain layers, each of which has a documentobject, as described in Chapter 31) The value of the documentproperty is the documentobject, which is not a displayable value Instead, you use the documentproperty as you build references

to properties and methods of the document and to other objects contained by the document, such as a form and its elements To load a different document into a win-dow, use the locationobject (see Chapter 17) The documentobject is described

in detail in Chapter 18

Related Items:documentobject

event

Only IE4+ treats the eventobject as a property of the windowobject Navigator 4+ and the W3C DOM pass an instance of the Eventobject as an argument to event handler functions The connection with the windowobject in IE is relatively incon-sequential, because all action involving the eventobject occurs in event handler functions The only difference is that the object can be treated as a more global

On the

CD-ROM

Tip

windowObject.event

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object when one event handler function invokes another Instead of having to pass

the eventobject parameter to the next function, IE functions can access the event

object directly (with or without the window.prefix in the reference)

For complete details about the eventobject in all browsers, see Chapter 29

Related Items:eventobject

external

The externalproperty (not implemented in IE5/Mac) is useful only when the

browser window is a component in another application The property provides a

gateway between the current browser window and the application that acts as a

host to the browser window component

With IE4+ acting as a component to the host operating system, the external

property can be used to access several methods that influence behaviors outside of

the browser Perhaps the three most useful methods to regular Web page scripters

are AddDesktopComponent(), AddFavorite(), and NavigateAndFind() The first

two methods display the same kind of alert dialog box that users get after making

these choices from the browser or desktop menus, so that you won’t be able to

sneak your Web site onto desktops or Favorites listings without the visitor’s

approval Table 16-2 describes the parameters for these three methods

Table 16-2 Popular window.external Object Methods

AddDesktopComponent(“URL”, Adds a Web site or image to the Active Desktop

“type”[, left, top, (if turned on in the user’s copy of Windows) The

image Dimensional parameters (optional) are all integer values.

AddFavorite(“URL”[, “title”]) Adds the specified URL to the user’s Favorites list

The optional title string parameter is how the URL should be listed in the menu (if missing, the URL appears in the list).

NavigateAndFind(“URL”,

“findString”, “target”) Navigates to the URL in the first parameter and

opens the page in the target frame (an empty string opens in the current frame) The

findStringis text to be searched for on that page and highlighted when the page loads.

windowObject.external

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