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

Availability

JavaScript 1.0

Synopsis

<input type="type"onchange="handler">
input.onchange

Description

The onchange property of an Input object specifies
an event handler function that is invoked when the user changes the
value displayed by a form element. Such a change may be an edit to
the text displayed in Text, Textarea, Password, or FileUpload
elements, or the selection or deselection of an option in a Select
element. Note that this event handler is only invoked when the user
makes such a change -- it is not invoked if a JavaScript program
changes the value displayed by an element.

Also note that the onchange handler is not invoked
every time the user enters or deletes a character in a text-entry
form element. onchange is not intended for that
type of character-by-character event handling. Instead,
onchange is invoked when the user's edit is
complete. The browser assumes that the edit is complete when keyboard
focus is moved from the current element to some other
element -- for example, when the user clicks on the next element
in the form. See the HTMLElement.onkeypress reference
page for character-by-character event notification.

The onchange event handler is not used by the
Hidden element or by any of the button elements. Those
elements -- Button, Checkbox, Radio, Reset, and Submit -- use
the onclick event handler instead.

The initial value of this property is a function that contains the
semicolon-separated JavaScript statements specified by the
onchange attribute of the HTML tag that defined
the object. When an event handler function is defined by an HTML
attribute, it is executed in the scope of
element rather than in the scope of the
containing window.

In the Netscape 4 event model, the onchange
handler function is passed an Event object as an argument. In the IE
event model, no argument is passed, but the applicable Event object
is available as the event property of the Window
object that contains the element.

See Also

HTMLElement.onkeypress; Chapter 19; Event,
EventListener, and EventTarget in the DOM reference section