Java Script notes

11/30/2011
1
JavaScript
JavaScript is the scripting language of the
Web.
JavaScript is used in millions of Web pages
to add functionality, validate forms, detect
browsers, and much more.
11/30/2011 1Hassan Khan
What is JavaScript?
JavaScript was designed to add interactivity to HTML
pages
JavaScript is a scripting language
A scripting language is a lightweight programming
language
JavaScript is usually embedded directly into HTML
pages
JavaScript is an interpreted language (means that
scripts execute without preliminary compilation)
Everyone can use JavaScript without purchasing a
license

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Example
<html>
<body>
<script type="text/javascript">
document.write("This is my first JavaScript!");
</script>
</body>
</html>
How to Handle Simple
Browsers
Browsers that do not support JavaScript, will display
JavaScript as page content.
The HTML comment tag should be used to "hide" the
JavaScript.
Just add an HTML comment tag  (end of comment) after
the last JavaScript statement.

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Example
The two forward slashes at the end of comment line (//) is
the JavaScript comment symbol. This prevents
JavaScript from executing the --> tag.
What can a JavaScript do?
JavaScript gives HTML designers a programming
tool
JavaScript can put dynamic text into an HTML page
JavaScript can react to events
JavaScript can read and write HTML elements
JavaScript can be used to validate data
JavaScript can be used to detect the visitor's
browser
JavaScript can be used to create cookies

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How To Use?
<script> tag is used to insert a JavaScript into
an HTML page.
Between <body> tag
Between <head> tag
How To Use (Cont.)?
JavaScripts in the body section will be
executed WHILE the page loads.
JavaScripts in the head section will be
executed when CALLED.

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JavaScript Statements
JavaScript is case sensitive.
Use of semicolon(;) in the end of statement is
optional.
document.write("Hello");
document.write("Hello")
JavaScript Comments
Single line comments start with //.
Multi line comments start with /* and end with
*/.

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JavaScript Variables
JavaScript variables are used to hold values
or expressions.
x=5, y=6, z=x+y
Rules for JavaScript variable names:
Variable names are case sensitive (y and Y
are two different variables)
Variable names must begin with a letter or
the underscore character
JavaScript Variables
Declaration
var x;
var carname;
Assign Values
x=5;
carname=“Toyota";

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JavaScript Arithmetic Operators
Y=5
JavaScript Assignment Operators
x = 5 and y=10

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+ Operator and Strings
To add two or more string variables together,
use the + operator.
Comparison Operators

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Logical Operators
If...Else Statements
used to perform different actions based on different
conditions.
if statement - use this statement to execute some
code only if a specified condition is true
if...else statement - use this statement to execute
some code if the condition is true and another code
if the condition is false
if...else if....else statement - use this statement to
select one of many blocks of code to be executed
switch statement - use this statement to select one
of many blocks of code to be executed

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Example (If)
Example (If...else)

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Example(If...else if...else)
Switch Statement
used to perform different actions based on
different conditions.

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Example (Switch)
Popup Boxes
Alert Box
alert(“Hello Every Body");
Confirm Box
confirm(“Press a button");
Prompt Box
prompt("Your name","")
11/30/2011 24
Hassan Khan

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Functions
A function will be executed by an event or by
a call to the function.
Example (Function)

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JavaScript Loops
You want the same block of code to run over and
over again in a row. Instead of adding several
almost equal lines in a script we can use loops to
perform a task like this.
In JavaScript, there are two different kind of loops:
for - loops through a block of code a specified
number of times
while - loops through a block of code while a
specified condition is true
The for Loop

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While Loop
The break Statement
The break statement will break the loop and
continue executing the code that follows after
the loop (if any).

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The continue Statement
The continue statement will break the current
loop and continue with the next value.
JavaScript Events
Events are actions that can be detected by
JavaScript.
Examples of events:
A mouse click
A web page or an image loading
Mousing over a hot spot on the web page
Selecting an input field in an HTML form
Submitting an HTML form
A keystroke

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Events
onLoad and onUnload
onFocus, onBlur and onChange
onSubmit
onMouseOver and onMouseOut
JavaScript Objects
JavaScript is an Object Oriented
Programming (OOP) language.
An OOP language allows you to define your
own objects and make your own variable
types.
We will start by looking at the built-in
JavaScript objects.

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JavaScript Objects and Properties
Properties are the values associated with an
object.
JavaScript String Object
The String object is used to manipulate a
stored piece of text.
Some String Methods
search()
toLowerCase()
toUpperCase()

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JavaScript Date Object
The Date object is used to work with dates
and times.
Data Comparison
?

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JavaScript Array Object
The Array object is used to store multiple
values in a single variable.
An array can be defined in three ways.
JavaScript Math Object
The Math object allows you to perform
mathematical tasks.
Math.PI
Math.E
Math.sqrt(number)
Math.round(4.7)

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JavaScript Navigator Object
The Navigator object allows you to
check/validate your Browser.
Navigator.appName,;
Navigator.appVersion

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