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

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JavaScript 1.0 Inherits from HTMLElement

Synopsis

document.form_name
document.forms[form_number]

Properties

Form
inherits properties from HTMLElement and defines or overrides the
following:

action

A read/write string (read-only in IE 3) that specifies the URL to
which the form data is sent when the form is submitted. The initial
value of this property is specified by the action
attribute of the <form> HTML tag. Usually,
this URL specifies the address as a CGI script, although it can also
be a mailto: or news: address.

elements[]

An array of input elements that appear in the form. Each element is a
Button, Checkbox, Hidden, Password, Radio, Reset, Select, Submit,
Text, or Textarea object. See the Form.elements[]
reference page.

encoding

A read/write string (read-only in IE 3) that specifies how form data
is encoded for transmission when the form is submitted. The initial
value of this property is specified by the enctype
attribute of the <form> tag. The default
value is "application/x-www-form-urlencoded", which is
sufficient for almost all purposes. Other values may sometimes be
necessary. For example, a value of "text/plain" is
convenient when the form is submitted by email to a
mailto: URL. See

CGI Programming on the
World Wide Web , by Shishir Gundavaram (O'Reilly),
for further information.

length

The number of elements in the form. Equivalent to
elements.length.

method

A read/write string (read-only in IE 3) that specifies the method by
which form data is submitted. The initial value of this property is
specified by the method attribute of the
<form> tag. The two legal values are
get and post.

The get method is the default. It is usually used
for form submissions such as database queries that do not have side
effects. With this method, the encoded form data is appended to the
URL specified by the Form.action property. The
post method is appropriate for form submissions,
such as additions to databases, that have side effects. With this
method, encoded form data is sent in the body of the HTTP request.

name

Specifies the name of the form. The initial value of this read/write
string property is the value of the name attribute
of the <form> tag.

target

A read/write string that specifies the name of the frame or window in
which the results of submitting a form should be displayed. Initially
specified by the target attribute. The special
names "_top", "_parent",
"_self", and "_blank" are also
supported for the target property and the
target attribute. See the
Form.target reference page.

Methods

Form inherits methods from HTMLElement and defines the following:

reset( )

Resets each of the input elements of the form to their default values.

submit( )

Submits the form.

Event Handlers

Form inherits event handlers from HTMLElement and defines the
following:

onreset

Invoked just before the elements of the form are reset. Specified in
HTML by the onreset attribute.

onsubmit

Invoked just before the form is submitted. Specified in HTML by the
onsubmit attribute. This event handler allows form
entries to be validated before being submitted.

HTML Syntax

A Form
object is created with a standard
HTML <form> tag. The form contains any input
elements created with the <input>,
<select>, and
<textarea> tags between
<form> and </form>:

<form
[ name="form_name" ]       // Used to name the form in JavaScript
[ target="window_name" ]   // The name of the window for responses
[ action="url" ]           // The URL to which the form is submitted
[ method=("get"|"post") ]  // The method of form submission
[ enctype="encoding" ]     // How the form data is encoded
[ onreset="handler" ]      // A handler invoked when form is reset
[ onsubmit="handler" ]     // A handler invoked when form is submitted
>
// Form text and input elements go here
</form> 

Description

The Form object represents an HTML <form> in
a document. Each form in a document is represented as an element of
the Document.forms[] array. Named forms are also
represented by the form_name property of
their document, where form_name is the
name specified in the name attribute of the
<form> tag.

The elements of a form (buttons, input fields, checkboxes, and so on)
are collected in the Form.elements[] array. Named
elements, like named forms, can also be referenced directly by
name -- the element name is used as a property name of the Form
object. Thus, to refer to a Text object element named
phone within a form named
questionnaire, you might use the JavaScript
expression:

document.questionnaire.phone

See Also

Button, Checkbox, FileUpload, Hidden, Input, Password, Radio, Reset,
Select, Submit, Text, Textarea; Chapter 15;
HTMLFormElement in the DOM reference section