The process of getting the element under the mouse is currently is currently browser dependent. This method (or, more precisely: the examples) has been
tested with Firefox 1, Netscape 6.2, and Netscape 7, and Internet Explorer 6
on Windows XP.
Steps that need to be done:
Write an event handler (a function) to handle mouse events.
Assign the function to intercept the desired mouse event(s).
Retrieve the element from within the event handler. When a mouse event is fired, the element which fires the
event will be one of the member of the event handler parameter.
Writing a mouse event handler function.
A mouse event handler function will be called whenever a certain mouse event is happening.
There are several kind of mouse
events, such as mouse move (onMouseMove), mouse over (onMouseOver),
mouse downs (onMouseDown), or mouse out (onMouseOut), among
others. All the mouse events accepts an implicit object as a
parameter. This parameter is an event object, which is passed
implicitly to the event handler. Within this event object,
there are some useful information, such as the mouse coordinates, and more
importantly, the element which fired the event. So, we can write
a generic event handler like this:
// do something
Assigning the event handler function
Assigning an event handler allows us to
'intercept' certain events and do something as a response to the event.
To assign the function as an event handler, simply assign the function to the desired mouse events.
Events are associated with elements. For
example, <TABLE onMouseMove=....> will be fired when the mouse is
moved over that TABLE element; and <TABLE onMouseOut=...> will be
fired when the mouse is moving outside that TABLE's boundary.
example, I am assigning the function so that I can intercept mouse downs (onMouseDown)
anywhere within the <BODY>
element. This means that if you click on any element inside the <BODY>,
the event handler will be executed.
Note that you can assign the event handler to any
Retrieving the element
As mentioned earlier, whenever
an event is fired, an event object is passed implicitly to the event handler. Within this event object,
there is a parameter. This parameter is a pointer to the
element that fired the event. In Internet Explorer, this parameter
while in Mozilla browsers (such as Netscape and Internet Explorer), it is:
Once you have access to the element, there
are many things that can be done with it. For starter, the sample code
below prints the nodeName of the element (nodeName is the html
tag of the element, such as "IMG", "TABLE",
// Internet Explorer
// Netscape and Firefox
else if (mEvent.target)
This page itself is a bit more complex, and I recommend you look at this
example first before trying to decipher this page.
Below are some more useful element
||A string containing the tag of the element, such as
"TABLE", "DIV", "IMG", etc.
||An element which is the parent node of the element.
For example, if you have <TABLE><TR><TD>cell</TD></TR></TABLE>,
the parent of <TD> is the <TR>; and the parent of the <TR>
||An element which is the first child node of the element.
||A string, which is the ID of the element. (The ID
must already be defined.)
So, there are many things that can be done with the
element. For example, you can retrieve the element type, the id, and
alter the style of the element, move it around, etc. Here's
an example of altering element color.
As you might have already noticed, when you move your mouse over any element on this
page, a popup bubble is displayed. The
popup bubble shows the element type of the element currently under
the mouse. It also shows the immediate parent node type. You
can move the mouse over any of the elements below and observe the
Another example: Printing DOM Tree of the
element under the mouse.
A <TABLE> element contains table rows <TR>,
table columns <TD>, and the table content, including text formatting
<FONT>, <B>, <ITALIC>, etc.
An <IMG> element:
A <FORM> element: