Java script session 3

JAVA SCRIPT
SESSION NO 3

11/25/2013

Developed By: Saif Ullah Dar

1

SESSION OBJECTIVES
1) Java Script Data Types.
2) Primitive Data Types.
3) Composite Data Types.
4) Trivial Data Types.
5) Java Script Variables.
6) Rules for Declaration of Variables
7) Java Script Keywords.
8) Scope of Variables.
9) Examples
10) Quiz
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2

JAVA SCRIPT DATA TYPES
• Data is the information and Data Types means the
ways in which we can retrieve the data.
• There are two Main types of the Data Types in Java
Script Language
1. Primitive Data Types
2. Composite Data Types

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JAVA SCRIPT DATA TYPES

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PRIMITIVE DATA TYPES
• JavaScript has three “primitive” types: number, string,
and Boolean
• Numbers are always stored as floating-point values
• Hexadecimal numbers begin with 0x
• Some platforms treat 0123 as octal, others treat it as
decimal

• Strings may be enclosed in single quotes or double
quotes
• Strings can contains n (newline), " (double quote), etc.

• Booleans are either true or false
• 0, "0", empty strings, undefined, null, and NaN are false ,
other values are true
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PRIMITIVE DATA TYPES

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COMPOSITE DATA TYPES
• A composite data type stores a collection of
multiple related values, unlike primitive data types.
• JavaScript supports a composite data type known
as objects, Functions, Arrays
• This will be discussed in the next Chapter in details.

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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.

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TRIVIAL DATA TYPES
JavaScript also defines two trivial data
types, null and undefined, each of which defines
only a single value.
The null keyword specifies that a variable does not
hold any value. (the null value is not equal to zero
because zero is a calculate value while null refers to
the absence of a value)

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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.

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DEFINING VARIABLES
<script type="text/javascript">
<!–
var money;
var name;
//-->
</script>

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<script type="text/javascript">
<!–
var money, name;
//-->
</script>


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RULES TO DEFINED VARIABLES
Java Script is a case-sensitive language.
These rules are that a variable name:
Can consist of digit, underscore, and alphabets.
Must begin with a letter or underscore character
Cannot begin with a number and cannot contain
any punctuation marks.
• Cannot contain any kind of special characters such
as +,*,%,and so on.
• Cannot contain spaces
• Cannot be a Java Script keyword
•
•
•
•
•

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VARIABLE INITIALIZATION
• Storing a value in a
variable is called variable
initialization.
• You can do variable
initialization at the time of
variable creation or 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 the time of
initialization as follows:
11/25/2013

<script
type="text/javascript">
<!–
var name = “Saif Ullah";
var money;
money = 2000.50;
//-->
</script>


13

JAVA SCRIPT IMPORTANT HINTS
• 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.
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JAVA SCRIPT KEYWORDS
• The following are reserved
words in JavaScript.
• They cannot be used as
JavaScript
variables, functions, metho
ds, loop labels, or any
object names.

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abstract
boolean
break
byte
case
catch
char
class
const
continue
debugg
er
default
delete
do
double


else
enum
export
extends
false
final
finally
float
for
function
goto
if
impleme
nts
import
in

instance
of
int
interface
long
native
new
null
package
private
protecte
d
public
return
short
static
super

switch
synchroni
zed
this
throw
throws
transient
true
try
typeof
var
void
volatile
while
with

15

ESCAPE SEQUENCES CHARACTERS


There are multiple escape sequence characters in JavaScript that
provides various kind of formatting.

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SCOPE OF VARIABLES
The scope of a variable is the region of your program in which
it is defined. JavaScript variable will have only two scopes.
a) Global Variables: A global variable has global scope which
means it is defined everywhere in your JavaScript code.
b) 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.

EXAMPLE OF DYNAMIC VARIABLES
• JavaScript has dynamic types.
• This means that the same variable
can be used as different types:
Example
var x;
// Now x is undefined
var x = 5;
// Now x is a Number
var x = “Saif Ullah Dar";
// Now x is a
String

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JAVA SCRIPT STRINGS
• A string is a variable which stores a series of
characters like “Saif Ullah Dar".
• A string can be any text inside quotes. You can
use single or double quotes:
Example
var carname="Volvo XC60";
var carname='Volvo XC60';
 You can use quotes inside a string, as long as they don't
match the quotes surrounding the string:

Example
var answer="It's alright";
var answer="He is called ‘Saif'";
var answer='He is called “Mr Dar"';
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JAVASCRIPT NUMBERS
• JavaScript has only one type of numbers.
• Numbers can be written with, or without decimals:
Example
var x1=34.00;
// Written with
decimals
var x2=34;
// Written without
decimals
 Extra large or extra small numbers can be written with scientific
(exponential) notation:
Example
var y=123e5;
var z=123e-5;

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// 12300000
// 0.00123


20

JAVA SCRIPT BOOLEANS
• Booleans can only have two values: true or false.
• Booleans are often used in conditional testing.
You will learn more about conditional testing in a
later chapter of this tutorial.

var x=true;
var y=false;

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<!DOCTYPE html>
<html>
<body>
<script>
var firstname;
firstname=“Saif";
document.write(firstname);
document.write("<br>");
firstname=“Ullah";
document.write(firstname);
</script>

<p>The script above declares a
variable,
assigns a value to it, displays the value,
changes the value,
and displays the value again.</p>
<body>
</html>
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QUIZ:1
Inside which HTML element do we put the JavaScript?
(1)<javascript>
(2)<js>
(3)<script>
(4)<scripting>

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ANS:1
Inside which HTML element do we put the JavaScript?
(1)<javascript>
(2)<js>
(3)<script>
(4)<scripting>

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QUIZ:2
What is the correct JavaScript syntax to write "Hello World"?
(1)document.write("Hello World");
(2)echo "Hello World";
(3)("Hello World");
(4)response.write("Hello World");

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ANS:2
What is the correct JavaScript syntax to write "Hello World"?
(1)document.write("Hello World");
(2)echo "Hello World";
(3)("Hello World");
(4)response.write("Hello World");

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26

THANK YOU
SAIF ULLAH DAR

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Java script session 3

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