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

Availability

JavaScript 1.0; enhanced in JavaScript 1.1

Synopsis

<a ... onclick="handler" ... >
<area ... onclick="handler" ... >
link.onclick

Description

The
onclick property of a Link object specifies an
event handler function that is invoked when the user clicks on the
link. The initial value of this property is a function that contains
the JavaScript statements specified by the onclick
attribute of the <a> or
<area> tag that defined the Link object.
When an event handler function is defined in this way by an HTML
attribute, it is executed in the scope of
element rather than in the scope of the
containing window.

The onclick event handler is invoked before the
browser follows the clicked hypertext link. This allows you to
dynamically set href, target,
and other properties of the link (using the this
keyword to refer to the clicked link). You may also use the methods
Window.alert( ), Window.confirm(
), and Window.prompt( ) from this event
handler.

In JavaScript 1.1, you may prevent the browser from following the
link by returning false. If you return
true, any other value, or nothing, the browser
follows the link as soon as onclick returns. You
might stop the browser from following a link if you use the
Window.confirm( ) method to ask the user if he
really wants to follow the link and the user chooses the

Cancel button, for example. In general, if you
want a link that performs some action but does not cause a new URL to
be displayed, it is better to use the onclick
event handler of a Button object instead of the
onclick handler of a Link object.

Note that while the onclick event handler returns
false to tell the browser not to perform its
default action (following a link), the onmouseover
event handler must return true to tell the browser
not to take its default action (displaying the URL of the link). This
incompatibility exists for historical reasons. The standard for Form
and form element event handlers is to return false
to prevent the browser from performing a default action.

In the Netscape 4 event model, the onclick 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 hypertext link.

Bugs

In Netscape 3, the onclick event handler of the
<area> does not work on Windows platforms. A
workaround is to specify a javascript: URL as the
value of the href attribute of the
<area> tag.

See Also

Chapter 19; EventListener, EventTarget, and
MouseEvent in the DOM reference section