JavaScript Bible, Gold Edition part 82 potx

UL Element Object For HTML element properties, methods, and event handlers, see Chapter 15.. Syntax Accessing UL element object properties and methods: IE4+ [window.]document.all.elemID.

The startproperty governs which number or letter begins the sequence of leading characters for nested LI items If the TYPEattribute specifies numbers, then the corresponding number is used; if it specifies letters, then the letter of the alpha-bet corresponding to the number becomes as the starting character You can change the numbering in the middle of a sequence via the LI.valueproperty

It is an extremely rare case that requires you to modify this property for an existing OL element But if your script is creating a new element for a segment of ordered list items that has some other content intervening from an earlier OL ele-ment, you can use the property to assign a starting value to the OL group

Example on the CD-ROM

Related Items:type, LI.valueproperties

type

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

An OL element can use any of five different numbering schemes Each scheme has a type code, whose value you can use for the typeproperty The following table shows the property values and examples:

The default value is 1 You are free to adjust the property after the table has ren-dered, and you can even stipulate a different type for specific LI elements nested inside (see the LI.typeproperty) If you want to have further nesting with a differ-ent numbering scheme, you can nest the OL elemdiffer-ents and specify the desired type for each nesting level, as shown in the following HTML example:

<OL TYPE=”A”>

<LI>One

<LI>Two

On the

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OL.type

<OL TYPE=”a”>

<LI>Sub One

<LI>Sub Two

<LI>Sub Three

</OL>

<LI>Four

</OL>

Indenting the HTML is optional, but it may help you to keep the nesting straight

Example on the CD-ROM

Related Items:start, UL.type, LI.typeproperties

UL Element Object

For HTML element properties, methods, and event handlers, see Chapter 15

compact†

type

†See OL Element Object.

Syntax

Accessing UL element object properties and methods:

(IE4+) [window.]document.all.elemID.property | method([parameters])

(IE5+/NN6) [window.]document.getElementById(“elemID”).property |

method([parameters])

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

About this object

The UL (unordered list) element is a container of LI (list item) elements An

unordered list means that the list items have no sequence and are preceded by

sym-bols that don’t signify any particular order The few element-specific attributes are

being deprecated in favor of style sheet definitions For the sake of backward

com-patibility with existing content, however, it is likely that many future generations of

browsers will continue to support these deprecated attributes These attributes are

therefore available as properties of the element object

On the

CD-ROM

UL

Most of the special appearance of a list (notably indentation) is handled auto-matically by the browser’s interpretation of how an ordered list should look You have control over the three possible characters that precede each item

Properties type

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

A UL element can use any of three different leading characters Each character type has a type code whose value you can employ for the typeproperty Property values are circle, disc, and square The difference between a circleand discis that the circleis unfilled, while the discis solid The default value is disc Example on the CD-ROM

Related Items:OL.type, UL.typeproperties

LI Element Object

For HTML element properties, methods, and event handlers, see Chapter 15

type value

Syntax

Accessing LI element object properties and methods:

(IE4+) [window.]document.all.elemID.property | method([parameters]) (IE5+/NN6) [window.]document.getElementById(“elemID”).property |

method([parameters])

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

On the

CD-ROM

LI

About this object

An LI (list item) element contains the HTML that is displayed for each item

within an OL or UL list Note that you can put any HTML you want inside a list item,

including images Attributes and properties of this element enable you to override

the specifications declared in the OL or UL containers (except in IE/Mac)

Properties

type

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

Because either an OL or UL container can own an LI element, the typeproperty

accepts any of the values that you assign to the typeproperties of both the OL and

UL element objects See the OL.typeand UL.typeproperties earlier in this chapter

for lists of those values

Exercise caution, however, if you attempt to mix and match types For example, if

you try to set the LI.typeproperty of an LI element to circleinside an OL

ele-ment, the results vary from browser to browser NN6, for example, follows your

command; however, IE may display some other characters

Example on the CD-ROM

Related Items:OL.type, UL.typeproperties

value

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

The valueproperty governs which number or letter is used for the current list

item inside an ordered list Employ this attribute and property to override the

natu-ral progression Because these sequence characters can be letters, numbers, or

Roman numerals, the integer you specify for this property is converted to the

num-bering scheme in force by the LI or OL element’s typeproperty

On the

CD-ROM

LI.value

Example on the CD-ROM

Related Item:OL.startproperty

DL, DT, and DD Element Objects

For HTML element properties, methods, and event handlers, see Chapter 15

compact†

†See OL Element Object.

Syntax

Accessing DL, DT, and DD element object properties and methods:

(IE4+) [window.] document.all.elemID.property | method([parameters]) (IE5+/NN6+) [window.] document.getElementById(“elemID”) property |

method([parameters])

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

About these objects

Three elements — DL, DT, and DD — provide context and (optionally) formatting for definitions in a document The DL element is the outer wrapper signifying a defi-nition list Each defidefi-nition term should be inside a DT element, while the defidefi-nition description should be in the nested DD element The HTML for a simple definition list has the following structure:

<DL>

<DT>First term

<DD>First term’s definition

<DT>Second term

<DD>Second term’s definition

</DL>

While there are no specific requirements for rendering definition lists by conven-tion, the term and description are usually on different lines with the description indented

All three of these elements are treated as element objects, sharing the same properties, methods, and event handlers of generic element objects The only one

On the

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DL

of the three that has anything special is the DL element, which has a compact

prop-erty IE4+ for Windows does respond to this attribute and property by putting the

description and term on the same line if the term is shorter than the usual

indenta-tion space of the descripindenta-tion

DIR and MENU Element Objects

For HTML element properties, methods, and event handlers, see Chapter 15

compact†

†See OL Element Object.

Syntax

Accessing DIR and MENU element object properties and methods:

(IE4+) [window.]document.all.elemID.property | method([parameters])

(IE5+/NN6) [window.]document.getElementById(“elemID”) property |

method([parameters])

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

About these objects

The DIR and MENU elements are treated in modern browsers as if they were UL

elements for unordered lists of items Both elements are deprecated in HTML 4.0;

yet, because they are acknowledged in that standard, they are also acknowledged

in the W3C DOM (and the IE DOM, too) Originally intended to assist in creating

sin-gle and double columns of text (long since supplanted by tables), usage of these

elements has fallen out of favor and is discouraged

DIR

The Navigator

and Other

Environment

Objects

Client-side scripting primarily focuses on the document

inside a browser window and the content of the

docu-ment As discussed in Chapter 16, the window, too, is an

important part of how you apply JavaScript on the client But

stepping out even one more level is the browser application

itself Scripts sometimes need to know about the browser and

the computing environment in which it runs so that they can

tailor dynamic content for the current browser and operating

system

To that end, browsers provide objects that expose as much

about the client computer and the browser as is feasible within

accepted principles of preserving a user’s privacy In addition

to providing some of the same information that CGI programs

on the server receive as environment variables, these

browser-level objects also include information about how well equipped

the browser is with regard to plug-ins and Java Another object

defined for NN4+ and IE4+ reveals information about the user’s

video monitor, which may influence the way your scripts

calcu-late information displayed on the page

The objects in this chapter don’t show up on the document

object hierarchy diagrams, except as freestanding groups (see

Appendix A) The IE4+ object model, however, incorporates

these environmental objects as properties of the window

object Because the windowreference is optional, you can

omit it for IE and wind up with a cross-browser, compatible

script in many cases

Where the IE (for Windows anyway) and NN environments

diverge significantly is in the way scripts can find out whether

a particular plug-in or support for a particular MIME type is

available in the current browser As you learn in this chapter,

28

In This Chapter

Determining which browser the user has Branching scripts according to the user’s operating system

Detecting plug-in support

the IE for Windows methodology can be a bit roundabout And yet the Macintosh version of IE5+ has adopted the approach initiated by NN3 Go figure

clientInformation Object (IE4+) and navigator Object (All)

appCodeName javaEnabled() appMinorVersion preference() appName taintEnabled() appVersion

browserLanguage cookieEnabled cpuClass language mimeTypes onLine oscpu platform plugins product productSub securityPolicy systemLanguage userAgent userLanguage userProfile vendor vendorSub

Syntax

Accessing clientInformationand navigatorobject properties and methods:

(All) navigator.property | method() (IE4+/NN6) [window.]navigator.property | method() (IE4+) [window.]clientInformation.property | method()

navigator

About this object

In Chapter 16, I repeatedly mention that the windowobject is the top banana of

the document object hierarchy In other programming environments, you likely can

find a level higher than the window — perhaps referred to as the application level.

You may think that an object known as the navigatorobject is that

all-encompass-ing object That is not the case, however

Although Netscape originally invented the navigatorobject for the Navigator 2

browser, Microsoft Internet Explorer also supports this object in its object model

For those who exhibit partisan feelings toward Microsoft, IE4+ provides an alternate

object —clientInformation— that acts as an alias to the navigatorobject You

are free to use the IE-specific terminology if your development is intended only for

IE browsers All properties and methods of the navigatorand

clientInformationobjects are identical In the rest of this section, all references

to the navigatorobject also apply to the clientInformationobject

Be aware that the number of properties for this object has grown with virtually

every browser version Moreover, other than some basic items that have been

around since the early days, most of the more recent properties are

browser-spe-cific Observe the compatibility ratings for each of the following properties very

carefully

Most of the properties of the navigatorobject deal with the browser program

the user runs to view documents Properties include those for extracting the

ver-sion of the browser and the platform of the client running the browser Because so

many properties of the navigatorobject are related to one another, I begin this

discussion by grouping four of the most popular ones together

Properties

appCodeName

appName

appVersion

userAgent

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

These four properties reveal just about everything that browser-sniffing code

needs to know about the user’s browser brand, version, and other tidbits Of these

four, only the last three are particularly valuable The first property in the list,

appCodeName, defines a class of client that encompasses essentially every standard

browser The value returned by browsers, Mozilla, is the code name of the first

browser engine on which NN and IE browsers at one time were based (the NCSA

Mosaic browser) This information does nothing to help your scripts distinguish

among browser flavors, so you can ignore the property But the other three

proper-ties are the ones with all the goodies

navigator.appCodeName