JavaScript to computer language learning the coding

JavaScript
Project Supervisor: Muzammil Hassan | Research Officer
Al-Khwarizmi Institute of
Computer Science (KICS)
Office: +92-42-9250245 | Fax: +92-42-9250246
Al-Khawarizmi Institute of Computer Science
(KICS) UET, Lahore
http://www.kics.edu.pk

About the Tutorial
JavaScript is a lightweight, interpreted programming language. It is designed for creating
network-centric applications. It is complimentary to and integrated with Java. JavaScript is
very easy to implement because it is integrated with HTML. It is open and cross-platform.
Audience
This tutorial has been prepared for JavaScript beginners to help them understand the
basic functionality of JavaScript to build dynamic web pages and web applications.
Prerequisites
For this tutorial, it is assumed that the reader have a prior knowledge of HTML coding. It
would help if the reader had some prior exposure to object-oriented programming concepts
and a general idea on creating online applications.

Table of Contents
About the Tutorial................................................................................................................ iii
Audience............................................................................................................................... iii
Prerequisites ......................................................................................................................... iii
1. Client Side Scripting Language ............................ 1
What is client-side and server-side?.......................................................................................1
2. JavaScript............................................................... 2
What is JavaScript?................................................................................................................2
Client-Side JavaScript............................................................................................................2
Advantages of JavaScript.......................................................................................................2
Limitations of JavaScript .......................................................................................................3
JavaScript Development Tools...............................................................................................3
3. Syntax...................................................................... 4
JavaScript Outputs..................................................................................................................4
Your First JavaScript Code ....................................................................................................4
Comments in JavaScript.........................................................................................................5
4. Variables................................................................. 6
JavaScript Datatypes ..............................................................................................................6
JavaScript Variables...............................................................................................................6
JavaScript Variable Scope......................................................................................................7
JavaScript Variable Names ....................................................................................................8
JavaScript Reserved Words....................................................................................................8
5. Objects In JavaScript ............................................ 9
Object Properties....................................................................................................................9
Object Methods ......................................................................................................................9
User-Defined Objects...........................................................................................................10
The new Operator.................................................................................................................10
The Object ( ) Constructor ...................................................................................................10
Defining Methods for an Object ..........................................................................................11
The ‘with’ Keyword.............................................................................................................12
Syntax...................................................................................................................................12
6. Functions............................................................... 14

Function Definition ..............................................................................................................14
Syntax ..............................................................................................................................14
Calling a Function................................................................................................................14
Function Parameters.............................................................................................................15
The return Statement ............................................................................................................16
Nested Functions..................................................................................................................17
Function () Constructor ........................................................................................................18
Function Literals ..................................................................................................................19
7. OPERATORS....................................................... 22
What is an Operator?............................................................................................................22
Arithmetic Operators............................................................................................................22
Comparison Operators..........................................................................................................23
Logical Operators.................................................................................................................25
Bitwise Operators.................................................................................................................26
Assignment Operators..........................................................................................................27
Miscellaneous Operators......................................................................................................29
Conditional Operator (? :)................................................................................................29
typeof Operator ................................................................................................................30
8. SWITCH-CASE ................................................... 31
Flow Chart............................................................................................................................31
Syntax...................................................................................................................................31
9. FOR LOOP........................................................... 34
The for Loop.........................................................................................................................34
Flow Chart .......................................................................................................................34
Syntax ..............................................................................................................................34
Example ...........................................................................................................................34
10. FOR-IN LOOP..................................................... 36
Syntax ..............................................................................................................................36
11. LOOP CONTROL ............................................... 38
The break Statement.............................................................................................................38
Flow Chart .......................................................................................................................38
Example ...........................................................................................................................38
The continue Statement........................................................................................................39

Using Labels to Control the Flow ........................................................................................40
Example 2 ........................................................................................................................41
12. WHILE LOOP ..................................................... 43
The while Loop ....................................................................................................................43
Flow Chart .......................................................................................................................43
The do...while Loop .............................................................................................................44
13. ERRORS AND EXCEPTIONS........................... 47
Syntax Errors........................................................................................................................47
Runtime Errors.....................................................................................................................47
Logical Errors.......................................................................................................................47
The try...catch Statement......................................................................................................47
The throw Statement ............................................................................................................48
Finally Statement..................................................................................................................50
The onerror( ) Method..........................................................................................................51
14. PAGE REDIRECT .............................................. 54
What is Page Redirection? ...................................................................................................54
JavaScript Page Refresh.......................................................................................................54
Auto Refresh ........................................................................................................................54
How Page Re-direction Works?...........................................................................................55
15. DIALOG BOX...................................................... 57
Alert Dialog Box ..................................................................................................................57
Confirmation Dialog Box.....................................................................................................58
Prompt Dialog Box...............................................................................................................59
16. jQuery and Its Plugins......................................... 61
What is jQuery?....................................................................................................................61
How to use jQuery?..............................................................................................................61
Local Installation .............................................................................................................61
CDN Based Version.........................................................................................................62

Client Side Scripting Language [1]
1. Client Side Scripting Language
Client-side scripting generally refers to the class of computer programs on the web that are
executed client-side, by the user's web browser, instead of server-side (on the web server).
What is client-side and server-side?
 Any machine can play the role of either a client or a server
 You could even have a machine being both
 Some languages, e.g. Javascript, are said to be client-side.
 Run on the user`s browser/web client
 Other languages, e.g. PHP, are said to be server-side.
 Run on the server that is delivering content to the user

JavaScript [2]
2. JavaScript
What is JavaScript?
Javascript is a dynamic computer programming language. It is lightweight and most
commonly used as a part of web pages, whose implementations allow client-side script to
interact with the user and make dynamic pages. It is an interpreted programming language
with object-oriented capabilities.
JavaScript was first known as LiveScript, but Netscape changed its name to JavaScript,
possibly because of the excitement being generated by Java. JavaScript made its first
appearance in Netscape 2.0 in 1995 with the name LiveScript. The general-purpose
core of the language has been embedded in Netscape, Internet Explorer, and other web
browsers.
The ECMA-262 Specification defined a standard version of the core JavaScript language.
• JavaScript is a lightweight, interpreted programming language.
• Designed for creating network-centric applications.
• Complementary to and integrated with Java.
• Complementary to and integrated with HTML.
• Open and cross-platform.
Client-Side JavaScript
Client-side JavaScript is the most common form of the language. The script should be
included in or referenced by an HTML document for the code to be interpreted by the
browser.
It means that a web page need not be a static HTML, but can include programs that interact
with the user, control the browser, and dynamically create HTML content.
The JavaScript client-side mechanism provides many advantages over traditional CGI server-
side scripts. For example, you might use JavaScript to check if the user has entered a valid e-
mail address in a form field.
The JavaScript code is executed when the user submits the form, and only if all the entries are
valid, they would be submitted to the Web Server.
JavaScript can be used to trap user-initiated events such as button clicks, link navigation, and
other actions that the user initiates explicitly or implicitly.
Advantages of JavaScript
The merits of using JavaScript are:
• Less server interaction: You can validate user input before sending the page off to the
server. This saves server traffic, which means less load on your server.
• Immediate feedback to the visitors: They don't have to wait for a page reload to see if
they have forgotten to enter something.

JavaScript [3]
• Increased interactivity: You can create interfaces that react when the user hovers over
them with a mouse or activates them via the keyboard.
• Richer interfaces: You can use JavaScript to include such items as drag- and-drop
components and sliders to give a Rich Interface to your site visitors.
Limitations of JavaScript
We cannot treat JavaScript as a full-fledged programming language. It lacks the following
important features:
• Client-side JavaScript does not allow the reading or writing of files. This has been
kept for security reason.
• JavaScript cannot be used for networking applications because there is no such
support available.
• JavaScript doesn't have any multithreading or multiprocessor capabilities. Once again,
JavaScript is a lightweight, interpreted programming language that
allows you to build interactivity into otherwise static HTML pages.
JavaScript Development Tools
One of major strengths of JavaScript is that it does not require expensive development tools.
You can start with a simple text editor such as Notepad. Since it is an interpreted language
inside the context of a web browser, you don't even need to buy a compiler.
To make our life simpler, various vendors have come up with very nice
JavaScript editing tools. Some of them are listed here:
• Microsoft FrontPage: Microsoft has developed a popular HTML editor called
FrontPage. FrontPage also provides web developers with a number of JavaScript tools to
assist in the creation of interactive websites.
• Macromedia Dreamweaver MX: Macromedia Dreamweaver MX is a very popular
HTML and JavaScript editor in the professional web development crowd. It provides
several handy prebuilt JavaScript
components, integrates well with databases, and conforms to new standards such as
XHTML and XML.
• Macromedia HomeSite 5: HomeSite 5 is a well-liked HTML and JavaScript
editor from Macromedia that can be used to manage personal websites effectively.

Syntax [4]
3. Syntax
JavaScript can be implemented using JavaScript statements that are placed within the
<script>... </script> HTML tags in a web page.
You can place the <script> tags, containing your JavaScript, anywhere within you web page,
but it is normally recommended that you should keep it within the <head> tags.
The <script> tag alerts the browser program to start interpreting all the text between these
tags as a script. A simple syntax of your JavaScript will appear as follows.
<script ...> JavaScript code
</script>
The script tag takes two important attributes:
• Language: This attribute specifies what scripting language you are using.
Typically, its value will be javascript. Although recent versions of HTML (and XHTML, its
successor) have phased out the use of this attribute.
• Type: This attribute is what is now recommended to indicate the scripting language in
use and its value should be set to "text/javascript".
So your JavaScript syntax will look as follows.
<script language="javascript" type="text/javascript"> JavaScript code
</script>
JavaScript Outputs
JavaScript can "display" data in different ways:
 Writing into an alert box, using window.alert().
 Writing into the HTML output using document.write().
 Writing into an HTML element, using innerHTML.
 Writing into the browser console, using console.log().
Your First JavaScript Code
Let us take a sample example to print out "Hello World".
This function can be used to write text, HTML, or both. Take a look at the following code.
<html>
<body>
<script language="javascript" type="text/javascript">
document.write("Hello World!")
</script>
</body>
</html>

Syntax [5]
Result
Comments in JavaScript
JavaScript supports both C-style and C++-style comments. Thus:
 Any text between a // and the end of a line is treated as a comment and is ignored by
JavaScript.
 Any text between the characters /* and */ is treated as a comment. This may span
multiple lines.
 JavaScript also recognizes the HTML comment opening sequence  is not recognized by JavaScript so it
should be written as //-->.
Example
The following example shows how to use comments in JavaScript.
<script language="javascript" type="text/javascript">

</script>

Variables [6]
4. Variables
JavaScript Datatypes
One of the most fundamental characteristics of a programming language is the set of data
types it supports. These are the type of values that can be represented and manipulated in a
programming language.
JavaScript allows you to work with three primitive data types:
• Numbers, e.g., 123, 120.50 etc.
• Strings of text, e.g. "This text string" etc.
• Boolean, e.g. true or false.
JavaScript also defines two trivial data types, null and undefined, each of which defines
only a single value. In addition to these primitive data types, JavaScript supports a composite
data type known as object. We will cover objects in detail in a separate chapter.
Note: Java does not make a distinction between integer values and floating- point values. All
numbers in JavaScript are represented as floating-point values. JavaScript represents numbers
using the 64-bit floating-point format defined by the IEEE 754 standard.
JavaScript Variables
Like many other programming languages, JavaScript has variables. Variables can be thought
of as named containers. You can place data into these containers and then refer to the data
simply by naming the container.
Before you use a variable in a JavaScript program, you must declare it. Variables are declared
with the var keyword as follows.
<script type="text/javascript">

</script>
You can also declare multiple variables with the same var keyword as
follows:

</script>
Storing a value in a variable is called variable initialization. You can do variable initialization
at the time of variable creation or at a later point in time when you need that variable.
For instance, you might create a variable named money and assign the value
2000.50 to it later. For another variable, you can assign a value at the time of initialization as
follows.

Variables [7]
Example

</script>
Note: Use the var keyword only for declaration or initialization, once for the life of any
variable name in a document. You should not re-declare same variable twice.
JavaScript is untyped language. This means that a JavaScript variable can hold a value of any
data type. Unlike many other languages, you don't have to tell JavaScript during variable
declaration what type of value the variable will hold. The value type of a variable can change
during the execution of a program and JavaScript takes care of it automatically.
JavaScript Variable Scope
The scope of a variable is the region of your program in which it is defined. JavaScript
variables have only two scopes.
• Global Variables: A global variable has global scope which means it can be defined
anywhere in your JavaScript code.
• Local Variables: A local variable will be visible only within a function where it is
defined. Function parameters are always local to that function.
Within the body of a function, a local variable takes precedence over a global variable with
the same name. If you declare a local variable or function parameter with the same
name as a global variable, you effectively hide the global variable. Take a look into the
following example.
<html>
<head>
<title>User-defined objects</title>
var myVar = "global"; // Declare a global variable
function checkscope() {
var myVar = "local"; // Declare a local variable
}
document.write(myVar);//if function will call then result will
local
</script>
</head>
<body>
</body>

Variables [8]
</html>
Result:
JavaScript Variable Names
While naming your variables in JavaScript, keep the following rules in mind.
 You should not use any of the JavaScript reserved keywords as a variable name.
These keywords are mentioned in the next section. For example, break or boolean
variable names are not valid.
 JavaScript variable names should not start with a numeral (0-9). They must begin
with a letter or an underscore character. For example, 123test is an invalid
variable name but _123test is a valid one.
 JavaScript variable names are case-sensitive. For example, Name and name are two
different variables.
JavaScript Reserved Words
A list of all the reserved words in JavaScript are given in the following table. They cannot be
used as JavaScript variables, functions, methods, loop labels, or any object names.
abstract
boolean
break
byte
case
catch
char
class
const
continue
debugger
default
delete
do
double
else
enum
export
extends
false
final
finally
float
for
function
goto
if
implements
import
in
Instanceof
int
interface
long
native
new
null
package
private
protected
public
return
short
static
super
switch
synchronized
this
throw
throws
transient
true
try
typeof
var
void
volatile
while
with

Objects In JavaScript [9]
5. Objects In JavaScript
JavaScript is an Object Oriented Programming (OOP) language. A programming language
can be called object-oriented if it provides four basic capabilities to developers:
• Encapsulation: the capability to store related information, whether data or methods,
together in an object.
• Aggregation: the capability to store one object inside another object.
• Inheritance: the capability of a class to rely upon another class (or number of classes)
for some of its properties and methods.
• Polymorphism: the capability to write one function or method that works in a variety
of different ways.
Objects are composed of attributes. If an attribute contains a function, it is considered to be a
method of the object, otherwise the attribute is considered a property.
Object Properties
Object properties can be any of the three primitive data types, or any of the abstract data
types, such as another object. Object properties are usually variables that are used internally
in the object's methods, but can also be globally visible variables that are used throughout the
page.
The syntax for adding a property to an object is:
objectName.objectProperty = propertyValue;
For example: The following code gets the document title using the "title" property of the
document object.
var str = document.title;
Object Methods
Methods are the functions that let the object do something or let something be done to it.
There is a small difference between a function and a method – at a function is a standalone
unit of statements and a method is attached to an object and can be referenced by the this
keyword.
Methods are useful for everything from displaying the contents of the object to the screen to
performing complex mathematical operations on a group of local properties and parameters.
For example: Following is a simple example to show how to use the
write() method of document object to write any content on the document.
document.write ("This is test");

User-Defined Objects
All user-defined objects and built-in objects are descendants of an object called
Object.
The new Operator
The new operator is used to create an instance of an object. To create an object, the new
operator is followed by the constructor method.
In the following example, the constructor methods are Object(), Array(), and
Date(). These constructors are built-in JavaScript functions.
var employee = new Object();
var books = new Array("C++", "Perl", "Java");
var day = new Date("August 15, 1947");
The Object ( ) Constructor
A constructor is a function that creates and initializes an object. JavaScript provides a special
constructor function called Object() to build the object. The return value of the Object()
constructor is assigned to a variable.
The variable contains a reference to the new object. The properties assigned to the object are
not variables and are not defined with the var keyword.
Example 1:
Try the following example; it demonstrates how to create an Object.
<html>
<head>
var book = new Object(); // Create the object book.subject
= "Perl"; // Assign properties to the object
book.author = "Mohtashim";
</script>
</head>
<body>
document.write("Book name is : " + book.subject + "<br>");
document.write("Book author is : " + book.author + "<br>");
</script>
</body>
</html>
Result

Example 2
This example demonstrates how to create an object with a User-Defined Function.
Here this keyword is used to refer to the object that has been passed to a function.
<html>
<head>
function book(title, author) {
this.title = title;
this.author = author;
}
</script>
</head>
<body>
var myBook = new book("Perl", "Mohtashim");
document.write("Book title is : " + myBook.title + "<br>");
document.write("Book author is : " + myBook.author +
"<br>");
</script>
</body>
</html>
Result
Defining Methods for an Object
The previous examples demonstrate how the constructor creates the object and assigns
properties. But we need to complete the definition of an object by assigning methods to it.
Example
Try the following example; it shows how to add a function along with an object.
<html>
<head>
// Define a function which will work as a method
function addPrice(amount) {
this.price = amount;

}
this.title = title; this.author = author;
this.addPrice = addPrice; // Assign that method as
property.
}
</script>
</head>
<body>
myBook.addPrice(100);
document.write("Book author is : " + myBook.author + "<br>");
document.write("Book price is : " + myBook.price + "<br>");
</script>
</body>
</html>
Result
The ‘with’ Keyword
The ‘with’ keyword is used as a kind of shorthand for referencing an object's properties or
methods.
The object specified as an argument to with becomes the default object for the duration of the
block that follows. The properties and methods for the object can be used without naming the
object.
Syntax
The syntax for with object is as follows:
with (object){
properties used without the object name and dot
}
Example
<html>
<head>
// Define a function which will work as a method

function addPrice(amount) {
with (this) {
price = amount;
}
}
this.title = title; this.author = author; this.price =
0;
this.addPrice = addPrice; // Assign that method as
property.
}
</script>
</head>
<body>
myBook.addPrice(100);
document.write("Book author is : " + myBook.author + "<br>");
document.write("Book price is : " + myBook.price + "<br>");
</script>
</body>
</html>
Result

Functions [14]
6. Functions
A function is a group of reusable code which can be called anywhere in your program. This
eliminates the need of writing the same code again and again. It helps programmers in writing
modular codes. Functions allow a programmer to divide a big program into a number of small
and manageable functions.
Like any other advanced programming language, JavaScript also supports all the features
necessary to write modular code using functions. You must have seen functions like alert()
and write() in the earlier chapters. We were using these functions again and again, but they
had been written in core JavaScript only once.
JavaScript allows us to write our own functions as well. This section explains how to write
your own functions in JavaScript.
Function Definition
Before we use a function, we need to define it. The most common way to define a function in
JavaScript is by using the function keyword, followed by a unique function name, a list of
parameters (that might be empty), and a statement block surrounded by curly braces.
Syntax
The basic syntax is shown here.
function functionname(parameterlist)
{
statements
}
</script>
Example
Try the following example. It defines a function called sayHello that takes no parameters:
<!DOCTYPE html>
<html>
<head>
<title>Funcations</title>
function sayHello() {
alert("Hello there");
}
</script>
</head>
<body>
<p>JavaScriot funcations</p>
</body>
</html>
Calling a Function
To invoke a function somewhere later in the script, you would simply need to write the name
of that function as shown in the following code.

Functions [15]
<html>
<head>
function sayHello() {
document.write("Hello there!");
}
</script>
</head>
<body>
<p>Click the following button to call the function</p>
<form>
<input type="button" onclick="sayHello()" value="Say
Hello">
</form>
<p>Use different text in write method and then try...</p>
</body>
</html>
Output (before Click):
Output (After Click):
Function Parameters
Till now, we have seen functions without parameters. But there is a facility to pass different
parameters while calling a function. These passed parameters can be captured inside the
function and any manipulation can be done over those parameters. A function can take
multiple parameters separated by comma.
Example
Try the following example. We have modified our sayHello function here. Now it takes two
parameters.
<html>
<head>
<title>Function Parameters</title>
function sayHello(name, age) {
document.write(name + " is " + age + " years old.");
}

Functions [16]
</script>
</head>
<body>
<form>
<input type="button" onclick="sayHello('Saqib Nazir', 24)"
value="Say Hello">
</form>
<p>Use different parameters inside the function and then
try...</p>
</body>
</html>
Output (Before Click):
Output(After click):
The return Statement
A JavaScript function can have an optional return statement. This is required if you want to
return a value from a function. This statement should be the last statement in a function.
For example, you can pass two numbers in a function and then you can expect the function to
return their multiplication in your calling program.
Example
Try the following example. It defines a function that takes two parameters and concatenates
them before returning the resultant in the calling program.
<html>
<head>
<title>The return Statement</title>
function concatenate(first, last) {
var full;
full = first + last;
return full;
}
function secondFunction() {
var result;
result = concatenate('Saqib ', 'Nazir');

Functions [17]
document.write(result);
}
</script>
</head>
<body>
<form>
<input type="button" onclick="secondFunction()"
value="Call Function">
</form>
<p>Use different parameters inside the function and then
try...</p>
</body>
</html>
There is a lot to learn about JavaScript functions, however we have covered the most
important concepts in this tutorial.
Nested Functions
Prior to JavaScript 1.2, function definition was allowed only in top level global code, but
JavaScript 1.2 allows function definitions to be nested within other functions as well. Still
there is a restriction that function definitions may not appear within loops or conditionals.
These restrictions on function definitions apply only to function declarations with the
function statement.
As we'll discuss later in the next chapter, function literals (another feature introduced in
JavaScript 1.2) may appear within any JavaScript expression, which means that they can
appear within if and other statements.
Example
Try the following example to learn how to implement nested functions.
<html>
<head>
<title>Funcation</title>

Functions [18]
function hypotenuse(a, b) {
function square(x) { return x * x; }
return Math.sqrt(square(a) + square(b));
}
var result;
result = hypotenuse(1, 2);
}
</script>
</head>
<body>
<form>
</form>
</body>
</html>
Function () Constructor
The function statement is not the only way to define a new function; you can define your
function dynamically using Function() constructor along with the new operator.
Note: Constructor is a terminology from Object Oriented Programming. You may not feel
comfortable for the first time, which is OK.
Syntax
Following is the syntax to create a function using Function() constructor along with the new
operator.
var variablename = new Function(Arg1, Arg2...,
"FunctionBody");
</script>

Functions [19]
The Function() constructor expects any number of string arguments. The last argument is the
body of the function – it can contain arbitrary JavaScript statements, separated from each
other by semicolons.
Notice that the Function() constructor is not passed any argument that specifies a name for
the function it creates. The unnamed functions created with the Function() constructor are
called anonymous functions.
Example
Try the following example.
<html>
<head>
<title>Function () Constructor</title>
var func = new Function("x", "y", "return x*y;");
var result;
result = func(10, 20);
}
</script>
</head>
<body>
<form>
</form>
</body>
</html>
Output (Before Click)
Output (After Click)
Function Literals
JavaScript 1.2 introduces the concept of function literals which is another new way of
defining functions. A function literal is an expression that defines an unnamed function.

Functions [20]
Syntax
The syntax for a function literal is much like a function statement, except that it is used as an
expression rather than a statement and no function name is required.
var variablename = function(Argument List){
Function Body
};
</script>
Syntactically, you can specify a function name while creating
a literal function as follows.
var variablename = function FunctionName(Argument List){
Function Body
};
</script>
But this name does not have any significance, so it is not worthwhile.
Example
Try the following example. It shows the usage of function literals.
<html>
<head>
<title>Function Literals</title>
var func = function (x, y) { return x * y };
var result;
result = func(10, 20);
}
</script>
</head>
<body>
<form>
</form>
</body>
</html>

Functions [21]

OPERATORS [22]
7. OPERATORS
What is an Operator?
Let us take a simple expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and ‘+’
is called the operator. JavaScript supports the following types of operators.
• Arithmetic Operators
• Comparison Operators
• Logical (or Relational) Operators
• Assignment Operators
• Conditional (or ternary) Operators
Let’s have a look at all the operators one by one.
Arithmetic Operators
JavaScript supports the following arithmetic operators: Assume variable A holds 10 and
variable B holds 20, then:
Operator Description Example
+ (Addition) Adds two operands Ex: A + B will give 30
- (Subtraction) Subtracts the second
operand from the first
Ex: A - B will give -10
* (Multiplication) Multiply both operands Ex: A * B will give 200
/ (Division) Divide the numerator by
the denominator
Ex: B / A will give 2
% (Modulus) Outputs the remainder
of an integer division
Ex: B % A will give 0
++ (Increment) Increases an integer
value by one
Ex: A++ will give 11
-- (Decrement) Decreases an integer
value by one
Ex: A-- will give 9
Note: Addition operator (+) works for Numeric as well as Strings. e.g. "a" + 10 will give
"a10".
Example
The following code shows how to use arithmetic operators in JavaScript.
<html>
<head>
<title>Arithmetic Operators
</title>
</head>
<body>
var a = 33;
var b = 10;
var c = "Test";
var linebreak = "<br />";
document.write("a + b = "); result = a + b;

OPERATORS [23]
document.write(linebreak);
document.write("a - b = "); result = a - b;
document.write(result); document.write(linebreak);
document.write("a / b = "); result = a / b;
document.write("a % b = "); result = a % b;
document.write("a + b + c = "); result = a + b + c;
a = a++; document.write("a++ = "); result = a++;
b = b--;
document.write("b-- = "); result = b--;
</script>
</body>
</html>
Output:
Comparison Operators
JavaScript supports the following comparison operators: Assume variable A holds 10 and
variable B holds 20, then:
== (Equal) Checks if the value of
two operands are equal
or not, if yes, then the
condition becomes true.
Ex: (A == B) is not true.
!= (Not Equal) Checks if the value of
two operands are equal
or not, if the values are
not equal, then the
Ex: (A != B) is true.
> (Greater than) Checks if the value of
the left operand is
greater than the value
ofthe right operand, if
yes, then the condition
becomes true.
Ex: (A > B) is not true.

OPERATORS [24]
< (Less than) Checks if the value of
the left operand is less
than the value of the
right operand, if yes,
then the condition
becomes true.
Ex: (A < B) is true.
>= (Greater than or
Equal to)
Checks if the value of
the left operand is
greater than or equal to
the value of the right
operand, if yes, then the
Ex: (A >= B) is not true.
<= (Less than or
Equal to)
Checks if the value of
the left operand is less
than or equal to the
value of the right
operand, if yes, then the
Ex: (A <= B) is true.
Example
The following code shows how to use comparison operators in JavaScript.
<html>
<head>
<title>Comparison Operators</title>
</head>
<body>
var a = 10;
var b = 20;
document.write("(a == b) => "); result = (a == b);
document.write("(a < b) => "); result = (a < b);
document.write("(a > b) => "); result = (a > b);
document.write("(a != b) => "); result = (a != b);
document.write("(a >= b) => "); result = (a >= b);
document.write("(a <= b) => "); result = (a <= b);
</script>
</body>
</html>

OPERATORS [25]
Output:
Logical Operators
JavaScript supports the following logical operators:
Assume variable A holds 10 and variable B holds 20, then:
&& (Logical AND) If both the operands are non-
zero, then the condition
becomes true.
Ex: (A && B) is true.
|| (Logical OR) If any of the two operands are
non-zero, then the condition
becomes true.
Ex: (A || B) is true.
! (Logical NOT) Reverses the logical state of its
operand. If a condition is true,
then the Logical NOT operator
will make it false.
Ex: ! (A && B) is false.
Example
<html>
<head>
<title>Logical Operators</title>
</head>
<body>
var a = true;
var b = false;
document.write("(a && b) => "); result = (a && b);
document.write("(a || b) => "); result = (a || b);
document.write("!(a && b) => "); result = (!(a && b));
</script>
</body>
</html>
Try the following code to learn how to implement Logical Operators in JavaScript.

OPERATORS [26]
Output:
Bitwise Operators
JavaScript supports the following bitwise operators: Assume variable A holds 2 and variable
B holds 3, then:
& (Bitwise AND) It performs a Boolean AND
operation on each bit of its
integer arguments.
Ex: (A & B) is 2.
| (BitWise OR) It performs a Boolean OR
operation on each bit of its
integer arguments.
Ex: (A | B) is 3.
^ (Bitwise XOR) It performs a Boolean exclusive
OR operation on each bit of its
integer arguments. Exclusive OR
means that either operand one is
true or operand two is true, but
not both.
Ex: (A ^ B) is 1.
~ (Bitwise Not) It is a unary operator and
operates by reversing all the bits
in the operand.
Ex: (~B) is -4.
<< (Left Shift) It moves all the bits in its first
operand to the left by the
number of places specified in the
second operand. New bits are
filled with zeros. Shifting a value
left by one position is equivalent
to multiplying it by 2, shifting
two positions is equivalent to
multiplying by 4, and so on.
Ex: (A << 1) is 4.
>> (Right Shift) Binary Right Shift Operator. The
left operand’s value is moved
right by the number of bits
specified by the right operand.
Ex: (A >> 1) is 1.
>>> (Right shift
with Zero)
This operator is just like the >>
operator, except that the bits
shifted in on the left are always
zero.
Ex: (A >>> 1) is 1.
Example
Try the following code to implement Bitwise operator in JavaScript.
<html>
<head>

OPERATORS [27]
<title>Bitwise Operators
</title>
</head>
<body>
var a = 2; // Bit presentation 10
var b = 3; // Bit presentation 11
document.write("(a & b) => "); result = (a & b);
document.write("(a | b) => "); result = (a | b);
document.write("(a ^ b) => "); result = (a ^ b);
document.write("(~b) => "); result = (~b);
document.write("(a << b) => "); result = (a << b);
document.write("(a >> b) => "); result = (a >> b);
</script>
</body>
</html>
Output
Assignment Operators
JavaScript supports the following assignment operators:
= (Simple
Assignment)
Assigns values from the right side operand
to the left side operand
Ex: C = A + B will
assign the value of
A + B into C
+= (Add and
Assignment)
It adds the right operand to the left
operand and assigns the result to the left
operand.
Ex: C += A is
equivalent to C =
C + A
-= (Subtract
and
Assignment)
It subtracts the right operand from the left
operand.
Ex: C -= A is
equivalent to C =
C - A

OPERATORS [28]
*= (Multiply
and
Assignment)
It multiplies the right operand with the left
operand.
Ex: C *= A is
equivalent to C =
C * A
/= (Divide
and
Assignment)
It divides the left operand with the right
operand.
Ex: C /= A is
equivalent to C =
C / A
%=
(Modules
and
Assignment)
It takes modulus using two operands and
assigns the result to the left operand.
Ex: C %= A is
equivalent to C =
C % A
Example
Try the following code to implement assignment operator in JavaScript.
<html>
<head>
<title>Assignment Operators
</title>
</head>
<body>
var a = 33;
var b = 10;
document.write("Value of a => (a = b) => ");
result = (a = b); document.write(result);
document.write("Value of a => (a += b) => ");
result = (a += b); document.write(result);
document.write("Value of a => (a -= b) => ");
result = (a -= b);
document.write("Value of a => (a *= b) => ");
result = (a *= b); document.write(result);
document.write("Value of a => (a /= b) => ");
result = (a /= b); document.write(result);
document.write("Value of a => (a %= b) => ");
result = (a %= b); document.write(result);
</script>
</body>
</html>

OPERATORS [29]
Output
Miscellaneous Operators
We will discuss two operators here that are quite useful in JavaScript: the conditional
operator (? :) and the typeof operator.
Conditional Operator (? :)
The conditional operator first evaluates an expression for a true or false value and then
executes one of the two given statements depending upon the result of the evaluation.
Operator Description
? : (Conditional ) If Condition is true? Then value X : Otherwise value Y
Example
Try the following code to understand how the Conditional Operator works in JavaScript.
<html>
<head>
<title>Conditional Operator (? :)
</title>
</head>
<body>
var a = 10;
var b = 20;
document.write("((a > b) ? 100 : 200) => "); result = (a > b)
? 100 : 200; document.write(result); document.write(linebreak);
document.write("((a < b) ? 100 : 200) => ");
result = (a < b) ? 100 : 200; document.write(result);
</script>
</body>
</html>
Output

OPERATORS [30]
typeof Operator
The typeof operator is a unary operator that is placed before its single operand, which can be
of any type. Its value is a string indicating the data type of the operand.
The typeof operator evaluates to "number", "string", or "boolean" if its operand is a number,
string, or boolean value and returns true or false based on the evaluation.
Here is a list of the return values for the typeof Operator.
Type String Returned by typeof
Number "number"
String "string"
Boolean "boolean"
Object "object"
Function "function"
Undefined "undefined"
Null "object"
Example
The following code shows how to implement typeof operator.
<html>
<head>
<title>typeof operator
</title>
</head>
<body>
var a = 10;
var b = "String";
result = (typeof b == "string" ? "B is String" : "B is
Numeric");
document.write("Result => "); document.write(result);
result = (typeof a == "string" ? "A is String" : "A is
Numeric");
document.write("Result => "); document.write(result);
</script>
</body>
</html>
Output

SWITCH-CASE [31]
8. SWITCH-CASE
You can use multiple if...else…if statements, as in the previous chapter, to perform a
multiway branch. However, this is not always the best solution, especially when all of the
branches depend on the value of a single variable.
You can use a switch statement which handles exactly this situation, and it does so more
efficiently than repeated if...else if statements.
Flow Chart
The following flow chart explains a switch-case statement works.
Syntax
The objective of a switch statement is to give an expression to evaluate and several different
statements to execute based on the value of the expression. The interpreter checks each case
against the value of the expression until a match is found. If nothing matches, a default
condition will be used.
switch (expression)

SWITCH-CASE [32]
{
case condition 1: statement(s)
break;
case condition 2: statement(s)
break;
...
case condition n: statement(s)
break;
default: statement(s)
}
The break statements indicate the end of a particular case. If they were omitted, the
interpreter would continue executing each statement in each of the following cases.
We will explain break statement in Loop Control chapter.
Example
Try the following example to implement switch-case statement.
<html>
<head>
<title>Switch
</title>
</head>
<body>
var grade = 'A';
document.write("Entering switch block<br />");
switch (grade) {
case 'A': document.write("Good job<br />");
break;
case 'B': document.write("Pretty good<br />");
break;
case 'C': document.write("Passed<br />");
break;
case 'D': document.write("Not so good<br />");
break;
case 'F': document.write("Failed<br />");
break;
default: document.write("Unknown grade<br />")
}
document.write("Exiting switch block");
</script>
</body>
</html>

SWITCH-CASE [33]
Output
Break statements play a major role in switch-case statements. Try the following code that
uses switch-case statement without any break statement.
<html>
<head>
<title>Switch
</title>
</head>
<body>
var grade = 'A';
document.write("Entering switch block<br />");
45
switch (grade) {
case 'A': document.write("Good job<br />"); case 'B':
document.write("Pretty good<br />"); case 'C':
document.write("Passed<br />");
case 'D': document.write("Not so good<br />"); case 'F':
document.write("Failed<br />"); default: document.write("Unknown
grade<br />")
}
document.write("Exiting switch block");
</script>
</body>
</html>
Output

FOR LOOP [34]
9. FOR LOOP
The for Loop
The ‘for’ loop is the most compact form of looping. It includes the following three important
parts:
• The loop initialization where we initialize our counter to a starting value. The
initialization statement is executed before the loop begins.
• The test statement which will test if a given condition is true or not. If the condition is
true, then the code given inside the loop will be executed, otherwise the control will
come out of the loop.
• The iteration statement where you can increase or decrease your counter.
You can put all the three parts in a single line separated by semicolons.
Flow Chart
The flow chart for loop in JavaScript would be as follows:
Syntax
The syntax of for loop is JavaScript is as follows:
for (initialization; test condition; iteration statement)
{
Statement(s) to be executed if test condition is true
}
Example
Try the following example to learn how a for loop works in JavaScript.
<html>
<head>
<title>For Loop
</title>

FOR LOOP [35]
</head>
<body>
var count;
document.write("Starting Loop" + "<br />");
for (count = 0; count < 10; count++) {
document.write("Current Count : " + count);
document.write("<br />");
}
document.write("Loop stopped!");
</script>
</body>
</html>
Output

FOR-IN LOOP [36]
10. FOR-IN LOOP
The for...in loop is used to loop through an object's properties. As we have not discussed
Objects yet, you may not feel comfortable with this loop. But once you understand how
objects behave in JavaScript, you will find this loop very useful.
Syntax
The syntax of ‘for..in’ loop is:
for (variablename in object){
statement or block to execute
}
In each iteration, one property from object is assigned to variablename and this loop
continues till all the properties of the object are exhausted.
Example
Try the following example to implement ‘for-in’ loop. It prints the web browser’s
Navigator object.
<html>
<head>
<title>For IN Loop
</title>
</head>
<body>
var aProperty;
document.write("Navigator Object Properties<br /> ");
for (aProperty in navigator) {
document.write(aProperty);
document.write("<br />");
}
document.write("Exiting from the loop!");
</script>
</body>
</html>

LOOP CONTROL [38]
11. LOOP CONTROL
JavaScript provides full control to handle loops and switch statements. There may be a
situation when you need to come out of a loop without reaching at its bottom. There may also
be a situation when you want to skip a part of your code block and start the next iteration of
the look.
To handle all such situations, JavaScript provides break and continue statements. These
statements are used to immediately come out of any loop or to start the next iteration of any
loop respectively.
The break Statement
The break statement, which was briefly introduced with the switch statement, is used to exit a
loop early, breaking out of the enclosing curly braces.
Flow Chart
Example
The following example illustrates the use of a break statement with a while loop. Notice how
the loop breaks out early once x reaches 5 and reaches to document.write (..) statement just
below to the closing curly brace:
<html>
<head>
<title>Break
</title>
</head>
<body>
var x = 1;
document.write("Entering the loop<br /> ");
while (x < 20) {
if (x == 5) {
break; // breaks out of loop completely

LOOP CONTROL [39]
}
x = x + 1;
document.write(x + "<br />");
}
document.write("Exiting the loop!<br /> ");
</script>
</body>
</html>
Output
We have already seen the usage of break statement inside a switch statement.
The continue Statement
The continue statement tells the interpreter to immediately start the next iteration of the
loop and skip the remaining code block. When a continue statement is encountered,
the program flow moves to the loop check expression immediately and if the condition
remains true, then it starts the next iteration, otherwise the control comes out of the loop.
Example
This example illustrates the use of a continue statement with a while loop. Notice how the
continue statement is used to skip printing when the index held in variable x reaches 5.
<html>
<head>
<title>Continue
</title>
</head>
<body>
var x = 1;
document.write("Entering the loop<br /> ");
while (x < 10) {
x = x + 1;
if (x == 5) {
continue; // skill rest of the loop body
}
document.write(x + "<br />");
}
</script>
</body>

LOOP CONTROL [40]
</html>
Output
Using Labels to Control the Flow
Starting from JavaScript 1.2, a label can be used with break and continue to control the flow
more precisely. A label is simply an identifier followed by a colon (:) that is applied to a
statement or a block of code. We will see two different examples to understand how to use
labels with break and continue.
Note: Line breaks are not allowed between the ‘continue’ or ‘break’ statement and its label
name. Also, there should not be any other statement in between a label name and associated
loop.
Try the following two examples for a better understanding of Labels.
Example 1
The following example shows how to implement Label with a break statement.
<html>
<head>
<title>Using Labels to Control the Flow
</title>
</head>
<body>
document.write("Entering the loop!<br /> ");
outerloop: // This is the label name
for (var i = 0; i < 5; i++) {
document.write("Outerloop: " + i + "<br />");
innerloop:
for (var j = 0; j < 5; j++) {
if (j > 3) break; // Quit the innermost
loop
if (i == 2) break innerloop; // Do the same
thing
if (i == 4) break outerloop; // Quit the outer
loop

LOOP CONTROL [41]
document.write("Innerloop: " + j + " <br />");
}
}
</script>
</body>
</html>
Output
Example 2
The following example shows how to implement Label with continue.
<html>
<head>
<title>Using Labels to Control the Flow
</title>
</head>
<body>
document.write("Entering the loop!<br /> ");
outerloop: // This is the label name
for (var i = 0; i < 3; i++) {
document.write("Outerloop: " + i + "<br />");
for (var j = 0; j < 5; j++) {
if (j == 3) {
continue outerloop;
}
document.write("Innerloop: " + j + "<br />");
}
}

LOOP CONTROL [42]
</script>
</body>
</html>
Output

WHILE LOOP [43]
12. WHILE LOOP
While writing a program, you may encounter a situation where you need to perform an action
over and over again. In such situations, you would need to write loop statements to reduce the
number of lines.
JavaScript supports all the necessary loops to ease down the pressure of programming.
The while Loop
The most basic loop in JavaScript is the while loop which would be discussed in this chapter.
The purpose of a while loop is to execute a statement or code block repeatedly as long as an
expression is true. Once the expression becomes false, the loop terminates.
Flow Chart
The flow chart of while loop looks as follows:
Syntax
The syntax of while loop in JavaScript is as follows:
while (expression){
Statement(s) to be executed if expression is true
}
Example
Try the following example to implement while loop.

WHILE LOOP [44]
<html>
<head>
<title>while Loop
</title>
</head>
<body>
var count = 0; document.write("Starting Loop "); while (count
< 10) {
document.write("Current Count : " + count + "<br />");
count++;
}
</script>
</body>
</html>
Output
The do...while Loop
The do...while loop is similar to the while loop except that the condition check happens at the
end of the loop. This means that the loop will always be executed at least once, even if the
condition is false.
Flow Chart
The flow chart of a do-while loop would be as follows:

WHILE LOOP [45]
Syntax
The syntax for do-while loop in JavaScript is as follows:
do{
Statement(s) to be executed;
} while (expression);
Note: Don’t miss the semicolon used at the end of the do...while loop.
Example
Try the following example to learn how to implement a do-while loop in JavaScript.
<html>
<head>
<title>while Loop
</title>
</head>
<body>
var count = 0;
document.write("Starting Loop" + "<br />");
do {
document.write("Current Count : " + count + "<br />");
count++;
} while (count < 5);
</script>

WHILE LOOP [46]
</body>
</html>
Output

ERRORS AND EXCEPTIONS [47]
13. ERRORS AND EXCEPTIONS
There are three types of errors in programming:
• Syntax Errors
• Runtime Errors
• Logical Errors
Syntax Errors
Syntax errors, also called parsing errors, occur at compile time in traditional programming
languages and at interpret time in JavaScript.
For example, the following line causes a syntax error because it is missing a closing
parenthesis.
window.print(;
</script>
When a syntax error occurs in JavaScript, only the code contained within the same thread as
the syntax error is affected and the rest of the code in other threads gets executed assuming
nothing in them depends on the code containing the error.
Runtime Errors
Runtime errors, also called exceptions, occur during execution (after
compilation/interpretation).
For example, the following line causes a runtime error because here the syntax is correct, but
at runtime, it is trying to call a method that does not exist.
window.printme();
</script>
Exceptions also affect the thread in which they occur, allowing other JavaScript threads to
continue normal execution.
Logical Errors
Logic errors can be the most difficult type of errors to track down. These errors are not the
result of a syntax or runtime error. Instead, they occur when you make a mistake in the logic
that drives your script and you do not get the result you expected.
You cannot catch those errors, because it depends on your business requirement what type of
logic you want to put in your program.
The try...catch Statement
The latest versions of JavaScript added exception handling capabilities. JavaScript
implements the try...catch construct as well as the throw operator to handle
exceptions.
You can catch programmer-generated and runtime exceptions, but you cannot catch
JavaScript syntax errors.

Here is the try...catch...finally block syntax:
try
{// Code to run
[break;]
}catch ( e ) {
// Code to run if an exception occurs
[break;]
}[ finally {
// Code that is always executed regardless of
// an exception occurring
}]
</script>
The try block must be followed by either exactly one catch block or one finally block (or one
of both). When an exception occurs in the try block, the exception is placed in e and the catch
block is executed. The optional finally block executes unconditionally after try/catch.
Example:
<!DOCTYPE html>
<html>
<head>
<title>Error
</title>
</head>
<body>
<p id="demo"></p>
<script>
try {
adddlert("Welcome guest!");
}
catch (err) {
document.getElementById("demo").innerHTML =
err.message;
}
</script>
</body>
</html>
Output:
The throw Statement
You can use a throw statement to raise your built-in exceptions or your customized
exceptions. Later these exceptions can be captured and you can take an appropriate action.

Example
The following example demonstrates how to use a throw statement.
<!DOCTYPE html>
<html>
<head>
<title>Finally Block
</title>
function myFunc() {
var a = 100;
var b = 0;
try {
if (b == 0) {
throw ("Divide by zero error.");
} else {
var c = a / b;
}
} catch (e) {
document.write("Error: " + e);
}
}
</script>
</head>
<body>
<p>Click the following to see the result:</p>
<form>
<input type="button" value="Click Me" onclick="myFunc();"
/>
</form>
</body>
</html>

You can raise an exception in one function using a string, integer, Boolean, or an object and
then you can capture that exception either in the same function as we did above, or in another
function using a try...catch block.
Finally Statement
You can use a finally block which will always execute unconditionally after the try/catch.
Here is an example.
Example:
<!DOCTYPE html>
<html>
<head>
<title>Finally Block
</title>
</head>
<body>
<p>Please input a number between 5 and 10:</p>
<input id="demo" type="text">
<button type="button" onclick="myFunction()">Test
Input</button>
<p id="message"></p>
<script>
function myFunction() {
var message, x;
message = document.getElementById("message");
message.innerHTML = "";
x = document.getElementById("demo").value;
try {
if (x == "") throw "is empty";
if (isNaN(x)) throw "is not a number";
x = Number(x);
if (x > 10) throw "is too high";
if (x < 5) throw "is too low";
}
catch (err) {
message.innerHTML = "Input " + err;
}
finally {
document.getElementById("demo").value = "";
}
}
</script>
</body>
</html>

Output when user enter less than 5:
Output when user enter more than 5:
Output when user enter any Character:
The onerror( ) Method
The onerror event handler was the first feature to facilitate error handling in JavaScript. The
error event is fired on the window object whenever an exception occurs on the page.
Example
<!DOCTYPE html>
<html>
<head>
<title>The onerror( ) Method
</title>
window.onerror = function () {
document.write("An error occurred.");
}
</script>
</head>
<body>
<form>

/>
</form>
</body>
</html>
The onerror event handler provides three pieces of information to identify the exact nature of
the error:
• Error message: The same message that the browser would display for the given error
• URL: The file in which the error occurred
• Line number: The line number in the given URL that caused the error
Here is the example to show how to extract this information.
Example
<!DOCTYPE html>
<html>
<head>
<title>The onerror( ) Method
</title>
window.onerror = function (msg, url, line) {
document.write("Message : " + msg); document.write("url :
" + url);
document.write("Line number : " + line);
}
</script>
</head>
<body>
<form>
/>
</form>

</body>
</html>
You can display extracted information in whatever way you think it is better.

PAGE REDIRECT [54]
14. PAGE REDIRECT
What is Page Redirection?
You might have encountered a situation where you clicked a URL to reach a page X but
internally you were directed to another page Y. It happens due to page redirection. This
concept is different from JavaScript Page Refresh.
There could be various reasons why you would like to redirect a user from the original page.
We are listing down a few of the reasons:
• You did not like the name of your domain and you are moving to a new one. In such a
scenario, you may want to direct all your visitors to the new site. Here you can
maintain your old domain but put a single page with a page redirection such that all
your old domain visitors can come to your new domain.
• You have built-up various pages based on browser versions or their names or
may be based on different countries, then instead of using your server-side page
redirection, you can use client-side page redirection to land your users on the
appropriate page.
• The Search Engines may have already indexed your pages. But while moving to
another domain, you would not like to lose your visitors coming through search
engines. So you can use client-side page redirection. But keep in mind this should not
be done to fool the search engine, it could lead your site to get banned.
JavaScript Page Refresh
You can refresh a web page using JavaScript location.reload method. This code can be called
automatically upon an event or simply when the user clicks on a link. If you want to refresh a
web page using a mouse click, then you can use the following code:
<a href="javascript:location.reload(true)">Refresh Page</a>
Auto Refresh
You can also use JavaScript to refresh the page automatically after a given time period. Here
setTimeout() is a built-in JavaScript function which can be used to execute another function
after a given time interval.
Example
Try the following example. It shows how to refresh a page after every 5 seconds. You
can change this time as per your requirement.
<html>
<head>
<title>Errorr</title>
<script type="text/JavaScript">
function AutoRefresh(t) {
setTimeout("location.reload(true);", t);
}
</script>
</head>
<body onload="JavaScript:AutoRefresh(5000);">

PAGE REDIRECT [55]
<p>This page will refresh every 5 seconds.</p>
</body>
</html>
How Page Re-direction Works?
The implementations of Page-Redirection are as follows.
Example 1
It is quite simple to do a page redirect using JavaScript at client side. To redirect your site
visitors to a new page, you just need to add a line in your head section as follows.
<html>
<head>
<title>How Page Re-direction Works?</title>
function Redirect() {
window.location = "http://www.kics.edu.pk";
}
</script>
</head>
<body>
<p>Click the following button, you will be redirected to home
page.</p>
<form>
<input type="button" value="Redirect Me"
onclick="Redirect();" />
</form>
</body>
</html>
Example 2

PAGE REDIRECT [56]
You can show an appropriate message to your site visitors before redirecting them to a new
page. This would need a bit time delay to load a new page. The following example shows
how to implement the same. Here setTimeout() is a built-in JavaScript function which can be
used to execute another function after a given time interval.
<html>
<head>
<title>How Page Re-direction Works?</title>
function Redirect() {
window.location = "http://www.kics.edu.pk";
}
document.write("You will be redirected to our main page in 10
seconds!");
setTimeout('Redirect()', 10000);
</script>
</head>
<body>
</body>
</html>
Output (Before Redirect)
Output (After Redirect)

DIALOG BOX [57]
15. DIALOG BOX
JavaScript supports three important types of dialog boxes. These dialog boxes can be used to
raise and alert, or to get confirmation on any input or to have a kind of input from the users.
Here we will discuss each dialog box one by one.
Alert Dialog Box
An alert dialog box is mostly used to give a warning message to the users. For example, if
one input field requires to enter some text but the user does not provide any input, then as a
part of validation, you can use an alert box to give a warning message.
Nonetheless, an alert box can still be used for friendlier messages. Alert box gives only one
button "OK" to select and proceed.
Example
<!DOCTYPE html>
<html>
<head>
<title>Alert Dialog Box
</title>
function Warn() {
alert("This is a warning message!");
document.write("This is a warning message!");
}
</script>
</head>
<body>
<p>Click the following button to see the result: </p>
<form>
<input type="button" value="Click Me" onclick="Warn();" />
</form>
</body>
</html>

DIALOG BOX [58]
Confirmation Dialog Box
A confirmation dialog box is mostly used to take user's consent on any option. It displays a
dialog box with two buttons: OK and Cancel.
If the user clicks on the OK button, the window method confirm() will return true. If the user
clicks on the Cancel button, then confirm() returns false. You can use a confirmation dialog
box as follows.
Example
<html>
<head>
<title>Confirmation Dialog Box
</title>
function getConfirmation() {
var retVal = confirm("Do you want to continue ?");
if (retVal == true) {
document.write("User wants to continue!");
return true;
} else {
Document.write("User does not want to continue!");
return false;
}
}
</script>
</head>
<body>
<form>
<input type="button" value="Click Me"
onclick="getConfirmation();" />
</form>
</body>
</html>

DIALOG BOX [59]
Output (Alert Appear)
Output (Click ok on Alert)
Prompt Dialog Box
The prompt dialog box is very useful when you want to pop-up a text box to get user input.
Thus, it enables you to interact with the user. The user needs to fill in the field and then click
OK.
This dialog box is displayed using a method called prompt() which takes two parameters: (i)
a label which you want to display in the text box and (ii) a default string to display in the text
box.
This dialog box has two buttons: OK and Cancel. If the user clicks the OK button, the
window method prompt() will return the entered value from the text box. If the user clicks the
Cancel button the window method prompt() returns null.
Example
The following example shows how to use a prompt dialog box:
<html>
<head>
<title>Confirmation Dialog Box
</title>
function getValue() {
var retVal = prompt("Enter your name : ", "your name
here");
document.write("You have entered : " + retVal);
}
</script>
</head>
<body>

DIALOG BOX [60]
<form>
<input type="button" value="Click Me"
onclick="getValue();" />
</form>
</body>
</html>
Output

jQuery and Its Plugins [61]
16. jQuery and Its Plugins
What is jQuery?
jQuery is a fast and concise JavaScript Library created by John Resig in 2006 with a nice
motto: Write less, do more. jQuery simplifies HTML document traversing, event handling,
animating, and Ajax interactions for rapid web development. jQuery is a JavaScript toolkit
designed to simplify various tasks by writing less code. Here is the list of important core
features supported by jQuery:
• DOM manipulation: The jQuery made it easy to select DOM elements, negotiate
them and modifying their content by using cross-browser open source selector engine
called Sizzle.
• Event handling: The jQuery offers an elegant way to capture a wide variety of
events, such as a user clicking on a link, without the need to clutter the HTML code
itself with event handlers.
• AJAX Support: The jQuery helps you a lot to develop a responsive and feature-rich
site using AJAX technology.
• Animations: The jQuery comes with plenty of built-in animation effects which you
can use in your websites.
• Lightweight: The jQuery is very lightweight library - about 19KB in size (Minified
and gzipped).
• Cross Browser Support: The jQuery has cross-browser support, and works well in
IE 6.0+, FF 2.0+, Safari 3.0+, Chrome and Opera 9.0+
• Latest Technology: The jQuery supports CSS3 selectors and basic XPath syntax.
How to use jQuery?
There are two ways to use jQuery.
• Local Installation: You can download jQuery library on your local machine and
include it in your HTML code.
• CDN Based Version: You can include jQuery library into your HTML code directly
from Content Delivery Network (CDN).
Local Installation
• Go to the https://jquery.com/download/ to download the latest version available.
• Now, insert downloaded jquery-2.1.3.min.js file in a directory of your website, e.g.
/jquery.
Example
<html>
<head>
<title>The jQuery Example</title>
<script type="text/javascript" src="/jquery/jquery-
2.1.3.min.js"></script>
$(document).ready(function () {
document.write("Hello, World!");
});

</script>
</head>
<body>
<h1>Hello</h1>
</body>
</html>
Now, you can include jquery library in your HTML file as follows:
CDN Based Version
You can include jQuery library into your HTML code directly from Content Delivery
Network (CDN). Google and Microsoft provides content deliver for the latest version.
We are using Google CDN version of the library throughout this tutorial.
Example
Now let us rewrite above example using jQuery library from Google CDN.
<html>
<head>
<script type="text/javascript"
src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.
js">
</script>
document.write("Hello, World!");
});
</script>
</head>
<body>
<h1>Hello</h1>
</body>
</html>
Output:

How to call a jQuery Library Functions?
As almost everything, we do when using jQuery reads or manipulates the document object
model (DOM), we need to make sure that we start adding events etc. as soon as the DOM is
ready.
If you want an event to work on your page, you should call it inside the $(document).ready()
function. Everything inside it will load as soon as the DOM is loaded and before the page
contents are loaded.
To do this, we register a ready event for the document as follows:
$(document).ready(function() {
// do stuff when DOM is ready
});
To call upon any jQuery library function, use HTML script tags as shown below:
<html>
<head>
<script type="text/javascript" src="jquery-2.1.4.min.js">
</script>
<script type="text/javascript" language="javascript">
$("div").click(function () {
alert("Hello world!");
});
});
</script>
</head>
<body>
<div id="newdiv">
Click on this to see a dialogue box.
</div>
</body>
</html>
Output:

jQuery slideDown() Method
The jQuery slideDown() method is used to slide down an element.
Syntax:
$(selector).slideDown(speed,callback);
The optional speed parameter specifies the duration of the effect. It can take the following
values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the sliding completes.
The following example demonstrates the slideDown() method:
Example:
<!DOCTYPE html>
<html>
<head>
<title>jQuery slideDown() Method
</title>
<script src="jquery-2.1.4.min.js"></script>
<script>
$("#flip").click(function () {
$("#panel").slideDown("slow");
});
});
</script>
<style>
#panel, #flip {
padding: 5px;
text-align: center;
background-color: #e5eecc;
border: solid 1px #c3c3c3;
}
#panel {
padding: 50px;
display: none;
}
</style>
</head>
<body>
<div id="flip">Click to slide down panel</div>
<div id="panel">Hello world!</div>
</body>
</html>

jQuery slideToggle() Method
The jQuery slideToggle() method toggles between the slideDown() and slideUp() methods.
If the elements have been slid down, slideToggle() will slide them up.
If the elements have been slid up, slideToggle() will slide them down.
$(selector).slideToggle(speed,callback);
The optional speed parameter can take the following values: "slow", "fast", milliseconds.
The optional callback parameter is a function to be executed after the sliding completes.
The following example demonstrates the slideToggle() method:
<!DOCTYPE html>
<html>
<head>
<title>jQuery slideToggle() Method
</title>
<script src="jquery-2.1.4.min.js"></script>
<script>
$("#flip").click(function () {
$("#panel").slideToggle("slow");
});
});
</script>
<style>

#panel, #flip {
padding: 5px;
text-align: center;
background-color: #e5eecc;
border: solid 1px #c3c3c3;
}
#panel {
padding: 50px;
display: none;
}
</style>
</head>
<body>
<div id="flip">Click to slide the panel down or up</div>
<div id="panel">Hello world!</div>
</body>
</html>
Output (Again Click):

JavaScript to computer language learning the coding

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