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

Availability

JavaScript 1.0 Inherits from Input, HTMLElement

Synopsis

form.name
form.elements[i]

Properties

FileUpload inherits properties from Input and HTMLElement and defines
or overrides the following:

value [ JavaScript 1.1]

A read-only string that specifies the filename entered by the user
into the FileUpload object. The user may enter a filename either by
typing it directly or by using the directory browser associated with
the FileUpload object.

To prevent malicious programs from uploading arbitrary files from the
client, this property may not be set by JavaScript code. Similarly,
the value attribute of the
<input> tag does not specify the initial
value for this property.

Methods

FileUpload inherits methods from Input and HTMLElement.

Event Handlers

FileUpload inherits event handlers from Input and HTMLElement and
defines or overrides the following:

onchange

Invoked when the user changes the value in the FileUpload element and
moves the keyboard focus elsewhere. This event handler is not invoked
for every keystroke in the FileUpload element, but only when the user
completes an edit.

HTML Syntax

A FileUpload element is created with a standard
HTML
<input> tag:

<form enctype="multipart/form-data"
method="post"> // Required attributes
...
<input
type="file" // Specifies that this is a FileUpload element
[ name="name" ]          // A name you can use later to refer to this element
// Specifies the name property
[ size="integer" ]       // How many characters wide the element is
[ maxlength="integer" ]  // Maximum allowed number of input characters
[ onblur="handler" ]     // The onblur(  ) event handler
[ onchange="handler" ]   // The onchange(  ) event handler
[ onfocus="handler" ]    // The onfocus(  ) event handler
>
...

Description

The FileUpload element represents a
file upload input element in a form. In many respects, this input
element is much like the Text element. On the screen, it appears like
a text input field with the addition of a

Browse button that opens a directory browser.
Entering a filename into a FileUpload element (either directly or
through the browser) causes Netscape to submit the contents of that
file along with the form. For this to work, the form must use
"multipart/form-data" encoding and the POST method.

The FileUpload element does not have a
defaultValue property and does not recognize the
value HTML attribute to specify an initial value
for the input field. Similarly, the value property
of the FileUpload element is read-only. Only the user may enter a
filename; JavaScript may not enter text into the FileUpload field in
any way. This is to prevent malicious JavaScript programs from
uploading arbitrary files (such as password files) from the
user's machine.

See Also

Form, HTMLElement, Input, Text; HTMLInputElement in the DOM reference
section