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# Option

An option in a selection list.

Client-side object |
Implemented in | JavaScript 1.0 JavaScript 1.1: added `defaultSelected` property; `text` property can be changed to change the text of an option

#### Created by

The `Option` constructor or the HTML `OPTION` tag. To create an `Option` object with its constructor:

    new Option([text[, value[, defaultSelected[, selected]]]])

Once you've created an Option object, you can add it to a selection list using the `Select.options` array.

#### Parameters

    text

Specifies the text to display in the select list.

    value

Specifies a value that is returned to the server when the option is selected and the form is submitted.

    defaultSelected

Specifies whether the option is initially selected (true or false).

    selected

Specifies the current selection state of the option (true or false).

#### Property Summary

Property | Description
--- | ---

    defaultSelected

Specifies the initial selection state of the option

    index

The zero-based index of an element in the `Select.options` array.

    length

The number of elements in the `Select.options` array.

    selected

Specifies the current selection state of the option

    text

Specifies the text for the option

    value

Specifies the value that is returned to the server when the option is selected and the form is submitted

#### Method Summary

This object inherits the `watch` and `unwatch` methods from `Object`.

#### Description

Usually you work with `Option` objects in the context of a selection list (a `Select` object). When JavaScript creates a `Select` object for each `SELECT` tag in the document, it creates `Option` objects for the `OPTION` tags inside the `SELECT` tag and puts those objects in the `options` array of the `Select` object. In addition, you can create new options using the `Option` constructor and add those to a selection list. After you create an option and add it to the `Select` object, you must refresh the document by using `history.go(0)`. This statement must be last. When the document reloads, variables are lost if not saved in cookies or form element values. You can use the `Option.selected` and `Select.selectedIndex` properties to change the selection state of an option.

- The `Select.selectedIndex` property is an integer specifying the index of the selected option. This is most useful for `Select` objects that are created without the `MULTIPLE` attribute. The following statement sets a `Select` object's `selectedIndex` property:

`document.myForm.musicTypes.selectedIndex = i`

- The `Option.selected` property is a Boolean value specifying the current selection state of the option in a `Select` object. If an option is selected, its `selected` property is true; otherwise it is false. This is more useful for `Select` objects that are created with the `MULTIPLE` attribute. The following statement sets an option's `selected` property to true:

`document.myForm.musicTypes.options[i].selected = true`

To change an option's text, use is `Option.text` property. For example, suppose a form has the following `Select` object:

    <SELECT name="userChoice">
       <OPTION>Choice 1
       <OPTION>Choice 2
       <OPTION>Choice 3
    </SELECT>

You can set the text of the `i`th item in the selection based on text entered in a text field named `whatsNew` as follows:

    myform.userChoice.options[i].text = myform.whatsNew.value

You do not need to reload or refresh after changing an option's text.

#### Examples

The following example creates two `Select` objects, one with and one without the `MULTIPLE` attribute. No options are initially defined for either object. When the user clicks a button associated with the `Select` object, the `populate` function creates four options for the `Select` object and selects the first option.

    <SCRIPT>
    function populate(inForm) {
       colorArray = new Array("Red", "Blue", "Yellow", "Green")

       var option0 = new Option("Red", "color_red")
       var option1 = new Option("Blue", "color_blue")
       var option2 = new Option("Yellow", "color_yellow")
       var option3 = new Option("Green", "color_green")

       for (var i=0; i < 4; i++) {
          eval("inForm.selectTest.options[i]=option" + i)
          if (i==0) {
             inForm.selectTest.options[i].selected=true
          }
       }

       history.go(0)
    }
    </SCRIPT>

    <H3>Select Option() constructor</H3>
    <FORM>
    <SELECT NAME="selectTest"></SELECT><P>
    <INPUT TYPE="button" VALUE="Populate Select List" onClick="populate(this.form)">
    <P>
    </FORM>

    <HR>
    <H3>Select-Multiple Option() constructor</H3>
    <FORM>
    <SELECT NAME="selectTest" multiple></SELECT><P>
    <INPUT TYPE="button" VALUE="Populate Select List" onClick="populate(this.form)">
    </FORM>

## defaultSelected

A Boolean value indicating the default selection state of an option in a selection list.

Property of | `Option`
Implemented in | JavaScript 1.1

#### Security

JavaScript 1.1. This property is tainted by default. For information on data tainting, see the Client-Side JavaScript Guide.

#### Description

If an option is selected by default, the value of the `defaultSelected` property is true; otherwise, it is false. `defaultSelected` initially reflects whether the `SELECTED` attribute is used within an `OPTION` tag; however, setting `defaultSelected` overrides the `SELECTED` attribute. You can set the `defaultSelected` property at any time. The display of the corresponding `Select` object does not update when you set the `defaultSelected` property of an option, only when you set the `Option.selected` or `Select.selectedIndex` properties. A `Select` object created without the `MULTIPLE` attribute can have only one option selected by default. When you set `defaultSelected` in such an object, any previous default selections, including defaults set with the `SELECTED` attribute, are cleared. If you set `defaultSelected` in a `Select` object created with the `MULTIPLE` attribute, previous default selections are not affected.

#### Examples

In the following example, the `restoreDefault` function returns the `musicType` `Select` object to its default state. The `for` loop uses the `options` array to evaluate every option in the `Select` object. The `if` statement sets the `selected` property if `defaultSelected` is true.

    function restoreDefault() {
       for (var i = 0; i < document.musicForm.musicType.length; i++) {
          if (document.musicForm.musicType.options[i].defaultSelected == true) {
             document.musicForm.musicType.options[i].selected=true
          }
       }
    }

The previous example assumes that the `Select` object is similar to the following:

    <SELECT NAME="musicType">
       <OPTION SELECTED> R&B
       <OPTION> Jazz
       <OPTION> Blues
       <OPTION> New Age
    </SELECT>

#### See also

`Option.selected`, `Select.selectedIndex`

## index

The zero-based index of an element in the `Select.options` array.

Property of | `Option`
Implemented in | JavaScript 1.0

#### Description

The `index` property specifies the position of an element in the `Select.options` array, starting with 0.

#### Examples

In the following example, the `getChoice` function returns the value of the `index` property for the selected option. The `for` loop evaluates every option in the `musicType` `Select` object. The `if` statement finds the option that is selected.

    function getChoice() {
       for (var i = 0; i < document.musicForm.musicType.length; i++) {
          if (document.musicForm.musicType.options[i].selected == true) {
             return document.musicForm.musicType.options[i].index
          }
       }
       return null
    }

The previous example assumes that the `Select` object is similar to the following:

    <SELECT NAME="musicType">
       <OPTION SELECTED> R&B
       <OPTION> Jazz
       <OPTION> Blues
       <OPTION> New Age
    </SELECT>

Note that you can also determine the index of the selected option in this example by using `document.musicForm.musicType.selectedIndex.`

## length

The number of elements in the `Select.options` array.

Property of | `Option`
Read-only |
Implemented in | JavaScript 1.0

#### Description

This value of this property is the same as the value of `Select.length`.

#### Examples

See `Option.index` for an example of the `length` property.

## selected

A Boolean value indicating whether an option in a `Select` object is selected.

Property of | `Option`
Implemented in | JavaScript 1.0

#### Security

JavaScript 1.1. This property is tainted by default. For information on data tainting, see the Client-Side JavaScript Guide.

#### Description

If an option in a `Select` object is selected, the value of its `selected` property is true; otherwise, it is false. You can set the `selected` property at any time. The display of the associated `Select` object updates immediately when you set the `selected` property for one of its options. In general, the `Option.selected` property is more useful than the `Select.selectedIndex` property for `Select` objects that are created with the `MULTIPLE` attribute. With the `Option.selected` property, you can evaluate every option in the `Select.options` array to determine multiple selections, and you can select individual options without clearing the selection of other options.

#### Examples

See the examples for `defaultSelected`.

#### See also

`Option.defaultSelected`, `Select.selectedIndex`

## text

A string specifying the text of an option in a selection list.

Property of | `Option`
Implemented in | JavaScript 1.0 JavaScript 1.1: The `text` property can be changed to updated the selection option. In previous releases, you could set the `text` property but the new value was not reflected in the `Select` object.

#### Security

JavaScript 1.1. This property is tainted by default. For information on data tainting, see the Client-Side JavaScript Guide.

#### Description

The `text` property initially reflects the text that follows an `OPTION` tag of a `SELECT` tag. You can set the `text` property at any time and the text displayed by the option in the selection list changes.

#### Examples

Example 1. In the following example, the `getChoice` function returns the value of the `text` property for the selected option. The `for` loop evaluates every option in the `musicType` `Select` object. The `if` statement finds the option that is selected.

    function getChoice() {
       for (var i = 0; i < document.musicForm.musicType.length; i++) {
          if (document.musicForm.musicType.options[i].selected == true) {
             return document.musicForm.musicType.options[i].text
          }
       }
       return null
    }

The previous example assumes that the `Select` object is similar to the following:

    <SELECT NAME="musicType">
       <OPTION SELECTED> R&B
       <OPTION> Jazz
       <OPTION> Blues
       <OPTION> New Age
    </SELECT>

Example 2. In the following form, the user can enter some text in the first text field and then enter a number between 0 and 2 (inclusive) in the second text field. When the user clicks the button, the text is substituted for the indicated option number and that option is selected.

The code for this example looks as follows:

    <SCRIPT>
    function updateList(theForm, i) {
       theForm.userChoice.options[i].text = theForm.whatsNew.value
       theForm.userChoice.options[i].selected = true
    }
    </SCRIPT>
    <FORM>
    <SELECT name="userChoice">
       <OPTION>Choice 1
       <OPTION>Choice 2
       <OPTION>Choice 3
    </SELECT>
    <BR>
    New text for the option: <INPUT TYPE="text" NAME="whatsNew">
    <BR>
    Option to change (0, 1, or 2): <INPUT TYPE="text" NAME="idx">
    <BR>
    <INPUT TYPE="button" VALUE="Change Selection"
    onClick="updateList(this.form, this.form.idx.value)">
    </FORM>

## value

A string that reflects the `VALUE` attribute of the option.

Property of | `Option`
Read-only |
Implemented in | JavaScript 1.0

#### Security

JavaScript 1.1. This property is tainted by default. For information on data tainting, see the Client-Side JavaScript Guide.

#### Description

When a `VALUE` attribute is specified in HTML, the `value` property is a string that reflects it. When a `VALUE` attribute is not specified in HTML, the `value` property is the empty string. The `value` property is not displayed on the screen but is returned to the server if the option is selected. Do not confuse the property with the selection state of the option or the text that is displayed next to it. The `selected` property determines the selection state of the object, and the `defaultSelected` property determines the default selection state. The text that is displayed is specified following the `OPTION` tag and corresponds to the `text` property.

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Last Updated: 05/28/99 12:00:06

Copyright (c) 1999 Netscape Communications Corporation