2. JavaScript
JavaScript is a lightweight scripting language
Embedded directly into HTML pages
JavaScript is an interpreted language (means
that scripts execute without preliminary
compilation)
Rajavel D JavaScript IITB-CSE-Internship 2013
3. What can a JavaScript do?
Client side data validation
React to event on html element
Read and write the html element
Put dynamic content on html pages
Creates the client side persistent (cookies, session )
Rajavel D JavaScript IITB-CSE-Internship 2013
5. JavaScript in <head>
<html> <head>
<script type="text/javascript">
function displayDate()
{ document.getElementById("demo").innerHTML=Date();
}
</script>
</head>
<body> <p id="demo"></p>
<button type="button" onclick="displayDate()">Display
Date</button>
</body> </html>
Rajavel D JavaScript IITB-CSE-Internship 2013
6. Using an External JavaScript
<head>
<script type="text/javascript" src=“myjavascript.js"></script>
</head>
JavaScript Statements
The semicolon is optional
Using semicolons makes it possible to write multiple statements
on one line.
Each statement is executed by the browser in the sequence
they are written
Rajavel D JavaScript IITB-CSE-Internship 2013
7. Comments and Popup Boxes
JavaScript Comments
Single line comments start with //.
Multi line comments start with /* and end with */.
JavaScript Popup Boxes
alert("I am an alert box!");
var r=confirm("Press a button");
r = true | false
var name=prompt("Please enter your name","");
Rajavel D JavaScript IITB-CSE-Internship 2013
8. JavaScript Events
onLoad and onUnload
onFocus, onBlur and onChange
OnSubmit
onMouseOver, onmousedown, onmouseout
Onerror
Onkeydown, onkeyup
onselect
Rajavel D JavaScript IITB-CSE-Internship 2013
9. Required Fields Validation
function validateForm()
{
var x=document.getElementById("txt").value
if (x==null || x=="")
{
alert("First name must be filled out");
return false;
}
}
Rajavel D JavaScript IITB-CSE-Internship 2013
10. E-mail Validation
function validateForm()
{
var x=document.forms["myForm"]["email"].value
var atpos=x.indexOf("@");
var dotpos=x.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length)
{
alert("Not a valid e-mail address");
return false;
}
}
Rajavel D JavaScript IITB-CSE-Internship 2013
12. JavaScript Cookies
A cookie is a variable that is stored on the
visitor's computer
With JavaScript, you can both create and
retrieve cookie values.
Rajavel D JavaScript IITB-CSE-Internship 2013
13. Create and Store a Cookie
function setCookie(c_name,value,exdays)
{
var exdate=new Date();
exdate.setDate(exdate.getDate() + exdays);
var c_value=escape(value) + ((exdays==null) ? "" : ";
expires="+exdate.toUTCString());
document.cookie=c_name + "=" + c_value;
}
Rajavel D JavaScript IITB-CSE-Internship 2013
14. Get a Cookie
function getCookie(c_name)
{
var i,x,y,Mycookies=document.cookie.split(";");
for (i=0;i<Mycookies.length;i++)
{
x=Mycookies[i].substr(0,Mycookies[i].indexOf("="));
y=Mycookies[i].substr(Mycookies[i].indexOf("=")+1);
if (x==c_name)
return unescape(y);
} }
Rajavel D JavaScript IITB-CSE-Internship 2013
15. Check Cookie
function checkCookie()
{
var username=getCookie("username");
if (username!=null && username!="")
alert("Welcome again " + username);
else
{ username=prompt("Please enter your name:","");
if (username!=null && username!="")
setCookie("username",username,365);
}
}
Rajavel D JavaScript IITB-CSE-Internship 2013