Radio

Object. A set of radio buttons on an HTML form. The user can use a set of radio to choose one item from a list.

HTML syntax

To define a set of radio buttons, use standard HTML syntax with the addition of JavaScript event handlers:

<INPUT
   TYPE="radio"
   NAME="radioName"
   VALUE="buttonValue"
   [CHECKED]
   [onBlur="handlerText"]
   [onClick="handlerText"]
   [onFocus="handlerText"]>
   textToDisplay

HTML attributes

NAME="radioName" specifies the name of the Radio object. All radio buttons in a group have the same NAME attribute. You can access this value using the name property, and you can use this name when indexing the elements array.

VALUE="buttonValue" specifies a value that is returned to the server when the radio button is selected and the form is submitted. This defaults to "on." You can access this value using the value property.

CHECKED specifies that the radio button is selected. You can access this value using the defaultChecked property.

textToDisplay specifies the label to display beside the radio button.

Syntax

To use a radio button's properties and methods:

1. radioName[index1].propertyName
2. radioName[index1].methodName(parameters)
3. formName.elements[index2].propertyName
4. formName.elements[index2].methodName(parameters)

Parameters

radioName is the value of the NAME attribute of a Radio object.

index1 is an integer representing a radio button in a Radio object.

formName is either the value of the NAME attribute of a Form object or an element in the forms array.

index2 is an integer representing a radio button on a form. The elements array contains an entry for each radio button in a Radio object.

propertyName is one of the properties listed below.

methodName is one of the methods listed below.

Implemented in

Navigator 2.0
Navigator 3.0: added type property; added blur and focus methods

Description

A Radio object on a form looks as follows:

A Radio object is a form element and must be defined within a <FORM> tag.

All radio buttons in a radio button group use the same name property. To access the individual radio buttons in your code, follow the object name with an index starting from zero, one for each button the same way you would for an array such as forms: document.forms[0].radioName[0] is the first, document.forms[0].radioName[1] is the second, and so on.

Properties

The Radio object has the following properties:


Property	Description
checked	Lets you programmatically select a radio button
defaultChecked	Reflects the CHECKED attribute
form property	Specifies the form containing the Radio object
length	Reflects the number of radio buttons in a Radio object
name	Reflects the NAME attribute
type	Reflects the TYPE attribute
value	Reflects the VALUE attribute

Methods

The Radio object has the following methods:


blur click eval	focus toString valueOf

Examples

Example 1. The following example defines a radio button group to choose among three music catalogs. Each radio button is given the same name, NAME="musicChoice," forming a group of buttons for which only one choice can be selected. The example also defines a text field that defaults to what was chosen via the radio buttons but that allows the user to type a nonstandard catalog name as well. The onClick event handler sets the catalog name input field when the user clicks a radio button.

<INPUT TYPE="text" NAME="catalog" SIZE="20">
<INPUT TYPE="radio" NAME="musicChoice" VALUE="soul-and-r&b"
   onClick="musicForm.catalog.value = 'soul-and-r&b'"> Soul and R&B
<INPUT TYPE="radio" NAME="musicChoice" VALUE="jazz"
   onClick="musicForm.catalog.value = 'jazz'"> Jazz
<INPUT TYPE="radio" NAME="musicChoice" VALUE="classical"
   onClick="musicForm.catalog.value = 'classical'"> Classical

Example 2. The following example contains a form with three text boxes and three radio buttons. The radio buttons let the user choose whether the text fields are converted to uppercase or lowercase, or not converted at all. Each text field has an onChange event handler that converts the field value depending on which radio button is checked. The radio buttons for uppercase and lowercase have onClick event handlers that convert all fields when the user clicks the radio button.

<HTML>
<HEAD>
<TITLE>Radio object example</TITLE>
</HEAD>
<SCRIPT>
function convertField(field) {
   if (document.form1.conversion[0].checked) {
      field.value = field.value.toUpperCase()}
   else {
   if (document.form1.conversion[1].checked) {
      field.value = field.value.toLowerCase()}
   }
}
function convertAllFields(caseChange) {
   if (caseChange=="upper") {
   document.form1.lastName.value = document.form1.lastName.value.toUpperCase()
   document.form1.firstName.value = document.form1.firstName.value.toUpperCase()
   document.form1.cityName.value = document.form1.cityName.value.toUpperCase()}
   else {
   document.form1.lastName.value = document.form1.lastName.value.toLowerCase()
   document.form1.firstName.value = document.form1.firstName.value.toLowerCase()
   document.form1.cityName.value = document.form1.cityName.value.toLowerCase()
   }
}
</SCRIPT>
<BODY>
<FORM NAME="form1">
<B>Last name:</B>
<INPUT TYPE="text" NAME="lastName" SIZE=20 onChange="convertField(this)">
<BR><B>First name:</B>
<INPUT TYPE="text" NAME="firstName" SIZE=20 onChange="convertField(this)">
<BR><B>City:</B>
<INPUT TYPE="text" NAME="cityName" SIZE=20 onChange="convertField(this)">
<P><B>Convert values to:</B>
<BR><INPUT TYPE="radio" NAME="conversion" VALUE="upper"
   onClick="if (this.checked) {convertAllFields('upper')}"> Upper case
<BR><INPUT TYPE="radio" NAME="conversion" VALUE="lower"
   onClick="if (this.checked) {convertAllFields('lower')}"> Lower case
<BR><INPUT TYPE="radio" NAME="conversion" VALUE="noChange"> No conversion
</FORM>
</BODY>
</HTML>

random

Method. Returns a pseudo-random number between zero and one. The random number generator is seeded from current time, as in Java.

Syntax

Math.random()

Implemented in

Navigator 2.0
Navigator 3.0: works on all platforms. In previous releases, it worked on Unix platforms only.

Examples

//Returns a random number between 0 and 1
function getRandom() {
   return Math.random()
}

referrer

Property. Specifies the URL of the calling document when a user clicks a link.

Syntax

document.referrer

Description

When a user navigates to a destination document by clicking a Link object on a source document, the referrer property contains the URL of the source document. Evaluate the referrer property from the destination document.

If the user clicked on a link to get to the current URL, referrer contains the URL the user linked from. referrer is empty if the user typed a URL in the Location box, or used some other means to get to the current URL. referrer is also empty if the server does not provide environment variable information.

referrer is a read-only property.

Examples

In the following example, the getReferrer function is called from the destination document. It returns the URL of the source document.

function getReferrer() {
   return document.referrer
}

refresh

Method. Makes newly installed plug-ins available, updates related arrays such as the plugins array, and optionally reloads open documents that contain plug-ins.

Syntax

navigator.plugins.refresh([true|false])

navigator.plugins.refresh(true)

reload

Method. Forces a reload of the window's current document.

Syntax

location.reload([true])

Parameters

true forces an unconditional HTTP GET of the document from the server. This should not be used unless you have reason to believe that disk and memory caches are off or broken, or the server has a new version of the document (possibly it is generated by a CGI on each request).

Description

The reload method forces a reload of the document specified by the URL in the location.href property.

This method uses the same policy that the Navigator's Reload button uses (Once per Session, Every Time, or Never). The user sets the default value of this policy by choosing Network Preferences from the Options menu and specifying Verify Documents on the Cache tab of the Preferences dialog box.

The reload method does not force a transaction with the server, unless the user has set the preference to Every Time, in which case it does a "conditional GET" request using an If-modified-since HTTP header, to ask the server to return the document only if its last-modified time is newer than the time the client keeps in its cache. In other words, reload will reload from the cache, unless the user has specified Every Time and the document has changed on the server since it was last loaded and saved in the cache.

In event handlers, you must specify window.location.reload() instead of simply using location.reload(). Due to the scoping of static objects in JavaScript, a call to location without specifying an object name is equivalent to document.location, which is a synonym for document.URL.

Examples

The following example displays an image and three radio buttons. The user can click the radio buttons to choose which image is displayed. Clicking another button lets the user reload the document.

<SCRIPT>
function displayImage(theImage) {
   document.images[0].src=theImage
}
</SCRIPT>

<FORM NAME="imageForm">
<B>Choose an image:</B>
<BR><INPUT TYPE="radio" NAME="imageChoice" VALUE="image1" CHECKED
   onClick="displayImage('seaotter.gif')">Sea otter
<BR><INPUT TYPE="radio" NAME="imageChoice" VALUE="image2"
   onClick="displayImage('orca.gif')">Killer whale
<BR><INPUT TYPE="radio" NAME="imageChoice" VALUE="image3"
   onClick="displayImage('humpback.gif')">Humpback whale

<BR>
<IMG NAME="marineMammal" SRC="seaotter.gif" ALIGN="left" VSPACE="10">

<P><INPUT TYPE="button" VALUE="Click here to reload"
   onClick="window.location.reload()">
</FORM>

replace

Method. Loads the specified URL over the current history entry.

Syntax

location.replace("URL")

Description

The replace method loads the specified URL over the current history entry, so after the replace method is used, the user cannot navigate to the previous URL by using Navigator's Back button.

In event handlers, you must specify window.location.replace() instead of simply using location.replace(). Due to the scoping of static objects in JavaScript, a call to location without specifying an object name is equivalent to document.location, which is a synonym for document.URL.

If your program will be run with JavaScript in Navigator 2.0, you could put the following line in a <SCRIPT> tag early in your program. This emulates replace, which was introduced in Navigator 3.0:

if (location.replace == null)
   location.replace = location.assign

The replace method does not create a new entry in the history list. To create an entry in the history list while loading a URL, use go.

Examples

The following example lets the user choose among several catalogs to display. The example displays two sets of radio buttons which let the user choose a season and a category, for example the Spring/Summer Clothing catalog or the Fall/Winter Home & Garden catalog. When the user clicks the Go button, the displayCatalog function executes the replace method, replacing the current URL with the URL appropriate for the catalog the user has chosen. Note that after the replace method is used, the user cannot navigate to the previous URL (the list of catalogs) by using Navigator's Back button.

<SCRIPT>
function displayCatalog() {
   var seaName=""
   var catName=""

   for (var i=0; i < document.catalogForm.season.length; i++) {
      if (document.catalogForm.season[i].checked) {
         seaName=document.catalogForm.season[i].value
         i=document.catalogForm.season.length
      }
   }

   for (var i in document.catalogForm.category) {
      if (document.catalogForm.category[i].checked) {
         catName=document.catalogForm.category[i].value
         i=document.catalogForm.category.length
      }
   }
   fileName=seaName + catName + ".html"
   location.replace(fileName)
}
</SCRIPT>

<FORM NAME="catalogForm">
<B>Which catalog do you want to see?</B>

<P><B>Season</B>
<BR><INPUT TYPE="radio" NAME="season" VALUE="q1" CHECKED>Spring/Summer
<BR><INPUT TYPE="radio" NAME="season" VALUE="q3">Fall/Winter

<P><B>Category</B>
<BR><INPUT TYPE="radio" NAME="category" VALUE="clo" CHECKED>Clothing
<BR><INPUT TYPE="radio" NAME="category" VALUE="lin">Linens
<BR><INPUT TYPE="radio" NAME="category" VALUE="hom">Home & Garden

<P><INPUT TYPE="button" VALUE="Go" onClick="displayCatalog()">
</FORM>

reset method

Method. Simulates a mouse click on a reset button for the calling form.

Syntax

formName.reset()

Parameters

formName is the name of any form or an element in the forms array.

Description

The reset method restores a form element's default values. A reset button does not need to be defined for the form.

Examples

The following example displays a Text object in which the user is to type "CA" or "AZ". The Text object's onChange event handler calls a function that executes the form's reset method if the user provides incorrect input. When the reset method executes, defaults are restored and the form's onReset event handler displays a message.

<SCRIPT>
function verifyInput(textObject) {
   if (textObject.value == 'CA' || textObject.value == 'AZ') {
      alert('Nice input')
   }
   else { document.form1.reset() }
}
</SCRIPT>

<FORM NAME="form1" onReset="alert('Please enter CA or AZ.')">
Enter CA or AZ:
<INPUT TYPE="text" NAME="state" SIZE="2" onChange=verifyInput(this)><P>
</FORM>

Reset object

Object. A reset button on an HTML form. A reset button resets all elements in a form to their defaults.

HTML syntax

To define a reset button, use standard HTML syntax with the addition of JavaScript event handlers:

<INPUT
   TYPE="reset"
   NAME="resetName"
   VALUE="buttonText"
   [onBlur="handlerText"]
   [onClick="handlerText"]
   [onFocus="handlerText"]>

HTML attributes

NAME="resetName" specifies the name of the Reset object. You can access this value using the name property, and you can use this name when indexing the elements array.

VALUE="buttonText" specifies the text to display on the button face. You can access this value using the value property.

Syntax

To use a Reset object's properties and methods:

1. resetName.propertyName
2. resetName.methodName(parameters)
3. formName.elements[index].propertyName
4. formName.elements[index].methodName(parameters)

Parameters

resetName is the value of the NAME attribute of a Reset object.

formName is either the value of the NAME attribute of a Form object or an element in the forms array.

index is an integer representing a Reset object on a form or the name of a Reset object as specified by the NAME attribute.

propertyName is one of the properties listed below.

methodName is one of the methods listed below.

Implemented in

Navigator 2.0
Navigator 3.0: added type property; added onBlur and onFocus event handlers; added blur and focus methods

Description

A Reset object on a form looks as follows:

A Reset object is a form element and must be defined within a <FORM> tag.

The reset button's onClick event handler cannot prevent a form from being reset; once the button is clicked, the reset cannot be canceled.

Properties

The Reset object has the following properties:


Property	Description
form property	Specifies the form containing the Reset object
name	Reflects the NAME attribute
type	Reflects the TYPE attribute
value	Reflects the VALUE attribute

Methods

The Reset object has the following methods:


blur click eval	focus toString valueOf

Examples

Example 1. The following example displays a Text object with the default value "CA" and a reset button with the text "Clear Form" displayed on its face. If the user types a state abbreviation in the Text object and then clicks the Clear Form button, the original value of "CA" is restored.

<B>State: </B><INPUT TYPE="text" NAME="state" VALUE="CA" SIZE="2">
<P><INPUT TYPE="reset" VALUE="Clear Form">

Example 2. The following example displays two Text objects, a Select object, and three radio buttons; all of these objects have default values. The form also has a reset button with the text "Defaults" on its face. If the user changes the value of any of the objects and then clicks the Defaults button, the original values are restored.

<HTML>
<HEAD>
<TITLE>Reset object example</TITLE>
</HEAD>
<BODY>
<FORM NAME="form1">
<BR><B>City: </B><INPUT TYPE="text" NAME="city" VALUE="Santa Cruz" SIZE="20">
<B>State: </B><INPUT TYPE="text" NAME="state" VALUE="CA" SIZE="2">
<P><SELECT NAME="colorChoice">
   <OPTION SELECTED> Blue
   <OPTION> Yellow
   <OPTION> Green
   <OPTION> Red
</SELECT>
<P><INPUT TYPE="radio" NAME="musicChoice" VALUE="soul-and-r&b"
   CHECKED> Soul and R&B
<BR><INPUT TYPE="radio" NAME="musicChoice" VALUE="jazz">
   Jazz
<BR><INPUT TYPE="radio" NAME="musicChoice" VALUE="classical">
   Classical
<P><INPUT TYPE="reset" VALUE="Defaults" NAME="reset1">
</FORM>
</BODY>
</HTML>

reverse

Method. Transposes the elements of an array: the first array element becomes the last and the last becomes the first.

Syntax

arrayName.reverse()

Parameters

arrayName is the name of an Array object or a property of an existing object.

Description

The reverse method transposes the elements of the calling array object.

Examples

The following example creates an array myArray, containing three elements, then reverses the array.

myArray = new Array("one", "two", "three")
myArray.reverse()

This code changes myArray so that:

myArray[0] is "three"
myArray[1] is "two"
myArray[2] is "one"

round

Method. Returns the value of a number rounded to the nearest integer.

Syntax

Math.round(number)

Parameters

number is any numeric expression or a property of an existing object.

Description

If the fractional portion of number is .5 or greater, the argument is rounded to the next highest integer. If the fractional portion of number is less than .5, the argument is rounded to the next lowest integer.

Examples

//Displays the value 20
document.write("The rounded value is " + Math.round(20.49))

//Displays the value 21
document.write("<P>The rounded value is " + Math.round(20.5))

//Displays the value -20
document.write("<P>The rounded value is " + Math.round(-20.5))

//Displays the value -21
document.write("<P>The rounded value is " + Math.round(-20.51))

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