Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript 1.0; enhanced in JavaScript 1.1

Inherits from/Overrides

Inherits from HTMLElement

Synopsis

select.options[i]

Constructor

In JavaScript 1.1, Option objects can be dynamically created with the
Option( ) constructor, as follows:

new Option(text, value, defaultSelected, selected)

Arguments

text

An optional string argument that specifies the
text property of the Option object.

value

An optional string argument that specifies the
value property of the Option object.

defaultSelected

An optional boolean argument that specifies the
defaultSelected property of the Option object.

selected

An optional boolean argument that specifies the
selected property of the Option object.

Properties

Option inherits the properties of HTMLElement and defines the
following:

defaultSelected

A
boolean that specifies whether the option is initially selected when
the Select object that contains it is created. This value is used to
restore a Select object to its initial state when the containing form
is reset. The initial value of this property is specified by the
selected attribute of the
<option> tag.

index

A read-only integer that specifies the
position or index of the option within the
options[] array of the Select object that contains
it. The first Option object in the array has its
index property set to 0. The second Option has an
index of 1, and so on.

selected

A read/write boolean value that specifies whether an option is
currently selected. You can use this property to test whether a given
option is selected and to select (by setting it to
true) or deselect (by setting it to
false) a given option. Note that when you select
or deselect an option in this way the Select.onchange(
) event handler is not invoked.

text

A string that specifies the text for the option that appears to the
user. The initial value of this property is whatever plain text
(without HTML tags) appears after the

<option>

tag and before the next

<option>,
</option>, or
</select> tag.

In JavaScript 1.0, the text property is read-only.
In JavaScript 1.1, it is read/write. By setting a new value for this
property, you can change the text that appears for the option within
its Select object. Note that if you plan to set this property in a
browser that cannot reflow document content, you should ensure that
changing the option label does not make the Select object wider. If
the object must become wider, ensure that no information to the right
of the Select object becomes obscured when it grows.

value

A read/write string that specifies the text passed to the web server
if the option is selected when the form is
submitted. The initial value of value is specified
by the value attribute of the
<option> tag. If the form is designed to be
submitted to a server (as opposed to simply being used by JavaScript
on the client side), each Option object within a Select object should
have a distinct value.

HTML Syntax

An Option object is created by an
<option> tag within a
<select>, which is within a
<form>. Multiple
<option> tags typically appear within the
<select>:

<form ...>
<select  ...>
<option
[ value="value" ]  // The value returned when the form is submitted
[ selected ] >     // Specifies whether this option is initially selected
plain_text_label       // The text to display for this option
[ </option> ]
...
</select>
...
</form>

Description

The Option object describes a single option displayed within a Select
object. The properties of this object specify whether it is selected
by default, whether it is currently selected, the position it has in
the options[] array of its containing Select
object, the text it displays, and the value it passes to the server
if it is selected when the containing form is submitted.

Note that although the text displayed by this option is specified
outside of the <option> tag, it must be
plain, unformatted text without any HTML tags so it can be properly
displayed in list boxes and drop-down menus that do not support HTML
formatting.

In JavaScript 1.1, you can dynamically create new Option objects for
display in a Select object with the Option( )
constructor. Once a new Option object is created, it can be appended
to the list of options in a Select object
s by assigning it to:

s.options[options.length]

See the Select.options[] reference page for details.

See Also

Select, Select.options[]; HTMLOptionElement and HTMLSelectElement in
the DOM reference section