Events Lecture Notes

JavaScript Events
Mrs.C.Santhiya
Assistant Professor
TCE,Madurai.

2
Event Object Properties
• Properties of Event Object contain event information
– clientX, clientY
– pageX, pageY
– screenX, screenY
– shiftKey, ctrlKey, altKey
– which
– Browsers differ in other properties of the Event Object
– target
– srcElement

3
Mouse events
Event Applies to Occurs when Handler
MouseDown Documents,
buttons, links
User depresses
a mouse button
onMouseDow
n
MouseUp Documents,
buttons, links
User releases a
mouse button
onMouseUp
Click Buttons, radio
buttons,
checkboxes,
submit
buttons, reset
buttons, links
User clicks a
form element
or link
onClick

4
MouseOver Links User moves
cursor over a
link
onMouseOver
MouseOut Areas, links User moves
cursor out of
an image map
or link
onMouseOut
Select Text fields,
text areas
User selects
form element’s
input field
onSelect

5
Key Board Events
KeyDown Documents,
images, links,
text areas
User depresses
a key
onKeyDown
KeyUp Documents,
images, links,
text areas
User releases a
key
onKeyUp
KeyPress Documents,
images, links,
text areas
User presses
or holds down
a key
onKeyPress
Change Text fields,
text areas,
select lists
User changes
the value of an
element
onChange

6
Focus Windows and
all form
elements
User gives
element input
focus
onFocus
Blur Windows and
all form
elements
User moves
focus to some
other element
onBlur
Reset Forms User clicks a
Reset button
onReset
Submit Forms User clicks a
Submit button
onSubmit

7
Sample Mouse events
• <h1 onmouseover="style.color='red'" onmouseout="style.color='black'">Mouse over this
text</h1>
- <head>
<script>
function myFunction(elmnt, clr) {
elmnt.style.color = clr;
}
</script>
</head> <p onmousedown="myFunction(this,'red')"
onmouseup="myFunction(this,'green')">
--<body onmousedown="whichElement(event)">

8
Mouse Event – Image Map
<!DOCTYPE html>
<html>
<head>
<script>
function writeText(txt) {
document.getElementById("desc").innerHTML = txt;
}
</script>
</head>
<body>
<img src ="planets.gif" width ="145" height ="126" alt="Planets" usemap="#planetmap" />
<map name="planetmap">
<area shape ="rect" coords ="0,0,82,126"
onmouseover="writeText('The Sun and the gas giant planets like Jupiter are by far the largest objects in our Solar System.')"
href ="sun.htm" target ="_blank" alt="Sun" />
<area shape ="circle" coords ="90,58,3"
onmouseover="writeText('The planet Mercury is very difficult to study from the Earth because it is always so close to the Sun.')"
href ="mercur.htm" target ="_blank" alt="Mercury" />
<area shape ="circle" coords ="124,58,8"
onmouseover="writeText('Until the 1960s, Venus was often considered a twin sister to the Earth because Venus is the nearest planet to us, and because
the two planets seem to share many characteristics.')"
href ="venus.htm" target ="_blank" alt="Venus" />
</map><p id="desc">Mouse over the sun and the planets and see the different descriptions.</p></body></html>

<HTML>
<HEAD>
<TITLE>Rollover</TITLE>
</HEAD>
<BODY>
<P ALIGN=RIGHT>
<A HREF="#" onMouseOver = "alert('Testing mouse over!');">
<FONT SIZE=12>Mouse over here!</FONT></A></P>
Some of the first interesting things you can do with JavaScript are event-driven. Event
driven means that a particular action causes something to happen. JavaScript has licks that
can detect events such as onClick, onMouseOver, onMouseOut. This page illustrates the
mouse over and mouse out events.<BR><BR><BR>
<A HREF="#"
onMouseOver="document.CISimage.src='CISa.gif';"
onMouseOut="document.CISimage.src='CISb.gif';">
<IMG SRC="CISa.gif" NAME="CISimage"></A>
<BR><BR>
In this case, the onMouseOver
will bring up an alert message
box . Note the use of quotes, the
semicolon and the parenthesis
which go with the alert()
function.
# in the A HREF
means same page.
CISaCISb.htmlCISaCISb.html
In this example onMouseOver
shows one image and onMouseOut
shows a different image. Note that
CISimage is the name associated
with the image that shows when
the code is loaded. Again, note the
use on quotation makes and semi-
colons and the < > in the HTML
surrounding the JavaScript.

<HTML>
<HEAD>
<TITLE>More events in JavaScript</TITLE>
<SCRIPT language="JavaScript">
var CISa_image = new Image();
CISa_image.src = "CISa.gif";
var CISb_image = new Image();
CISb_image.src = "CISb.gif";
</SCRIPT>
The word var is optional - however if used it should be lower case.
When I write this program with VAR I get an error in explorer about missing ; which
essentially means their is a problem with the code.
</HEAD>
<BODY>
The code above preloads two images.<BR>
<A HREF="#"
onMouseOver="CISimage.src='CISa.gif';"
onMouseOut="CISimage.src='CISb.gif';">
<IMG SRC="CISb.gif" NAME="CISimage" BORDER = 0></A>
</BODY>
</HTML>
CISaCISb1.htmlCISaCISb1.html
Load the images. The
variable name where they
are put are CISa_image and
CISb_image.
This time the CISb.gif is
loaded when the form is shown.
In this example I am simply giving
the image name.

<HTML>
<HEAD>
<TITLE>Java rotate</TITLE>
<SCRIPT>
originalz = new Image;
originalz.src="house.jpg";
flipz = new Image;
flipz.src = "houseusd.jpg";
</SCRIPT>
</HEAD>
<BODY bgcolor=beige>
<DIV ALIGN=CENTER>
<H1>Here is an image to roll the mouse over</H1>
<H3>Rolling the mouse over and out are called events.</H3>
<A HREF="javamouse.html"
onMouseOver="document.myhouse.src = flipz.src"
onMouseOut="document.myhouse.src = originalz.src">
<IMG SRC="house.jpg"
NAME="myhouse"></A>
</DIV>
</BODY>
</HTML>
javamouse.htmljavamouse.html
This code establishes a new Image called
originalz and then specifies the source for this
image as house.jpg.
It then establishes another new image called flipz
and then specifies that the source for this image is
houseusd.jpg.
The events are associated with the A HREF which refers
to this page. The events say take the current document or
window and then the name associated with the image and
make the source the sources that were specified in the
<HEAD>.
This means
the original
image shown
is house.jpg
Document refers to the
object of the window that is
being worked with.
Note I
used
the
defined
image
name
and not
the .jpg
name.

<A HREF="tryevent1.html"
onMouseOver="alert('Testing events...')">ALERT MOUSE TEST!</A>
This slide shows the result of
moving the mouse over the
ALERT MOUSE TEST. The
code behind this line is shown
below.

onMouseOver="document.bgColor='beige'">CHANGE BACKGROUND TO BEIGE!</A>
This shows the results of running
the mouse over CHANGE
BACKGROUND TO BEIGE!
The code is shown below.
Note that “document.bgcolor=‘beige’” is enclosed in double quotes
and the word ‘beige’ is enclosed in single quotes because it is
embedded in double quotes and trying to use double quotes would
confuse the structure of the command.

onMouseOver="window.status='Testing roll over'; return true"
onMouseOut="window.status='Testing roll out'; return true">WINDOW STATUS TRUE TEST!</A>

21
Load Events
function todaytxt() {
var Today=new Date();
return today.getMonth()+1+”/”+Today.getDate()+”/”+Today.
getFullYear();
}
current
date

24
Onresize
<!DOCTYPE html>
<html>
<head>
<script>
function myFunction() {
var w = window.outerWidth;
var h = window.outerHeight;
var txt = "Window size: width=" + w + ", height=" + h;
document.getElementById("demo").innerHTML = txt;
}
</script>
</head>
<body onresize="myFunction()">
<p>Try to resize the browser window.</p>
<p id="demo"> </p>
</body>
</html>

25
Input Events
<script>
function myFunction() {
var x = document.getElementById("fname");
x.value = x.value.toUpperCase();
}
</script>
</head>
<body>
Enter your name: <input type="text" id="fname" onblur="myFunction()">
</body>

26
html><head>
<title>Simple JavaScript Button</title>
<script language=“JavaScript"></script>
</head>
<body>
<h1>Simple JavaScript Button</h1>
<form>
<input type=“button"
value="Don't Click Me"
onClick="dontClick()">
</form>
</body></html>

27
<html><html>
<head><head>
<title>onerror event handler example</title><title>onerror event handler example</title>
<script language=“JavaScript”><script language=“JavaScript”>
Function errorHandler(){Function errorHandler(){
alert(“an error has ocurred”);alert(“an error has ocurred”);
}}
window.onerror = errorHandler;window.onerror = errorHandler;
</script></script>
</head></head>
<body><body>
<script language=“JavaScript”><script language=“JavaScript”>
document.write(“errorHandler()”);document.write(“errorHandler()”);
</script></script>
</body></body>
</html></html>

28
<script>
function preferedBrowser() {
prefer = document.forms[0].browsers.value;
alert("You prefer browsing internet with " + prefer);
}
</script>
<body>
<form>
Choose which browser you prefer:
<select id="browsers" onchange="preferedBrowser()">
<option value="Chrome">Chrome</option>
<option value="Internet Explorer">Internet Explorer</option>
<option value="Firefox">Firefox</option>
</select>
</form></body></html>

29
<script>
function myFunction(x) {
x.style.background = "yellow";
}
</script>
</head>
<body>
•Enter your name: <input type="text" onfocus="myFunction(this)">

30
<script>
function color(color) {
document.forms[0].myInput.style.background = color;
}
</script>
</head>
<body>
<form>
Write a message:<br>
<input type="text“ onkeydown="color('yellow')“ onkeyup="color('white')“ name="myInput">
</form>

31
Others
<head>
<script>
function whichButton(event) {
document.getElementById("demo").innerHTML = event.keyCode;
}
</script>
</head> <body onkeyup="whichButton(event)"><p id="demo"></p>

32
<script>
function show_coords(event) {
document.getElementById("demo").innerHTML =
"X= " + event.clientX + "<br>Y= " + event.clientY;
}
</script>
•<p onmousedown="show_coords(event)">
•<p id="demo"></p>

33
Type representation &validation
<script>
function getEventType(event) {
document.getElementById("demo").innerHTML = event.type;
}
</script>
<p id=demo onmousedown="getEventType(event)"></p>
Client Side Validation
– Phone: /^(?(d{3}))?[- ]?(d{3})[- ]?(d{4})$/
– Email: /^[0-9a-zA-Z]+@[0-9a-zA-Z]+[.]{1}
[0-9a-zA-Z]+[.]?[0-9a-zA-Z]+$/
– Currency: /^s*(+|-)?((d+(.dd)?)|(.dd))s*$/

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