What is scripting language?

first defination- a language which can be used to enhance routines of an operating system
		shell script, bash script, perl
second defination - a language which is not a proper language, it is subset of a programming language, used for  a specific purpose only
		javascript,vbscript,jscript

in case of javascript ,we use second defination only


Why we need to learn client side scripting
a server has to server request of numerous clients, 
for which it uses its resources such as ram,processor,hdd etc.

a client side script may help to reduce load on server. 
by doing some processings at client side if possible, 
by using resources of client such as ram,processor, hdd


we can classify work done by javascript in 5 categories
1. client side validation
	data at client side can be validated for
		a. pattern
			ascii values
			regex
		b. range
	if only valid data is passed to server
	server load is reduced


2. client side calculation
	used in shopping carts
	all shopping cart calculations can be done using javascript, only checkouts (payment) are validated by server side script

3. dhtml
	Dynamic HTML
	it is not generating dynamic web content
	it is just dynamic presentation of web content

	slide shows
	menu popup
	news tickers

	it is combination of	html+css+javascript


4. browser properties usage
	identifying web browser
	resolution identification
	adding a page to bookmarks/favourites
	set a page as homepage(client side)
	cookies can also be managed using javascript
	
5. ajax




====================================================
Javascript code is embeded within html page

<script language='javascript'>

</script>
	

or

<script type='text/javascript'>

</script>

or

<script>

</script>

Why we learn javascript only and not other client side scripting languages

javascript	started by netscape navigator
		now maintained by sun-oracle

		w3c conformance rule for standard 
		web browsers to support it
		i.e. all browsers do support it

		syntaxes resemble c programming

jscript		started and maintained by Microsoft
		no such rule,only IE supports it

		syntaxes resemble c programming

vbscript	started and maintained by Microsoft
		no such rule,only IE supports it

		syntaxes resemble vb programming
=====================================================
output statement
	document.write("");


concatenation operator is +
	when atleast one operand is non numeric
	if both operands are numeric, it would be 	addition
	
	s="1";
	r="1";
	t=s+r;
	t="11"

dialog box
1. alert 
	is used to deliver critical message
	user cant continue to browse, without reading ths message
	it has only single button, ok
	alert("Message");


2. confirm 
	it is used for boolean input
            Sy:-confirm (" Message");
	it has two buttons
	ok		true
	cancel		false
	
3. prompt
	is used for string input
	it can also be used for numeric input
	prompt("Message","default value");
========================================================
syntax for defining a function in javascript


	function is a keyword

	function function_name([parameters])
	{

	[return]
	}

	as javascript is loosely typed,
	data types are not specified
	
	function add(x,y)
	{
	return x+y;
	}
========================================================
universe.milkyway.solarsystem.earth.asia.india.mp.bhopal.indrapuri.sectorc.plot275.class5

	document object model

to fetch html form data in javascript
	by name attribute
x=document.all.formname.fieldname.value;
	to assign value by name attribute
document.all.formname.fieldname.value=n


	by id attribute
x=document.getElementById('id').value;
	to assign
document.getElementById('id').value=n;



----------------------------------------------------------------------------
JavaScript Display Possibilities

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().