Java script basic

JavaScript Basics
ADMEC MULTIMEDIA
Leader in Animation & Digital Media Education
ISO 9001:2008 CERTIFIED | ADOBE Testing Center
www.admecindia.co.in

Content
i. What is JavaScript?
ii. Use of JavaScript?
iii. Features of JavaScript
Popups
Variable
Scopes
Function
iv. DATATYPE in JavaScript
Number
String
Undefined
Boolean
Null
v. Operators in JavaScript
Assignment Operator
Equality Operator
Strict Equality Operators

What is JavaScript?
JavaScript is scripting/programming language. File
Extension of JavaScript is ".js”. This extension can be catched
by a number of applications including Windows Script Host,
Dreamweaver MX, Notepad, Netscape Navigator, PavScrip,
UltraEdit.
JavaScript is also considered as "assembly language of the
web". JavaScript is totally user based. It is does not store any
in-built data or function.
JavaScript is object oriented. We can also create small objects
with help of basic JavaScript.

Use of JavaScript?
JavaScript is also used to make websites rich and
dynamic. Almost every website have JavaScript used in
it. It tells how JavaScript important for us.
There are plenty of websites and applications which are
using JavaScript such as: Gmail, Google, YouTube,
Yahoo, LinkedIn, Twitter, Facebook etc...

Features of JavaScript
POPUPS
Popup is additional display box/window surprisingly
comes over web browser with information & notice.
• Alert: Is any notice to the viewer & provide only
option to "OK" after reading.
Example:
alert('welcome to js');
• Confirm: It is useful to display any of information/
message to viewer which let them decide for
accepting & rejecting information with option of
"OK" & "CANCEL“
Example:
confirm('Are u sure to visit this page?');

• Prompt: Take input (info/text/massage/name--
alphabetic value) from Viewers.
Example:
prompt('Enter ur name plz');

VARIABLE:
Variable is a kind of container with limited space where
we can put value (Numeric, String, Boolean [true/false],
objects etc) just for one time if we try to put 2nd value
1st will automatically eliminate. Variable can be
identified with unique names.
Variable are restricted with some special characters
(symbols) like we can only use underscore (_), dollar ($)
and Alpha Numeric character.
The right way to write variables
var myNum = 45;
var my_num = 55;
var num1 = 11;
var num = 78

SCOPES:
Scope is set of Variable, objects and Function you can
use. (Local & Global)
Maintain accessibility through variable & function.
There are 2 Variable used: Local Variable & Global
Variable
In Local Scope, Variable is declared within the Function
whereas Global Scope, Variable is Declared Outside the
function.
Data remain secure if we used local Variable.

FUNCTION:
A function is a group of reusable code which enables a
programmer to create a code that is in better
organization and execution and which can be called
anywhere in your program. In short function eliminates
the repetitive writing of same codes.
Function helps a programmer to divide a big program
into a number of small chunks of program and also
helps in managing functions easily & effectively.
The most common way to define a function in JavaScript
is by using the keyword “function”.

Syntax of function:
function main() //head of the function, these brackets () are
called parenthesis
{
//body of the function
}
Types of function: Named Function & Anonymous Function
Examples:
Named function:
function main()
{
}
Note: declared a 'main' function. The name of the function is
'main'.

Unnamed function:
var main = function ()
{
}
Note: Declared an unnamed function and at the same time
assigned to a variable 'main'. You can't declare a function
without the name so you need to store that in a variable. This
type of declaring method of function known as 'closure' in
JavaScript.

DATATYPE in JavaScript
There 5 Primitive Datatypes given below:
Number:
 A JavaScript programmer all the time have to deal with
numbers. It is a value and we use it in various operations in
the application or website. Some times you can't get the
expected result and either your program gets broken or
filled with errors because of non-numeric types of values.
 JavaScript offers main 3 functions to convert any of the
value to number.
 Numbers can be written with or without decimals.

Example:
var num = 10.25;
1. alert(Number(num)); //10.25
2. alert(parseInt(num)); //10
3. alert(parseFloat(num)); //10.25
String:
 String (value) is used to represent text related data. String
is also a set of “element” of 16-bit unsigned integer value
which start from the first element is ZERO and the next is
ONE and so on at index.
 We can use string literals in scripts by enclosing them in
single or double quotation marks e.g. (‘ ’, “ ”).

Example:
Single Quotation Mark
alert('you clicked on CANCEL');
Double Quotation Mark
alert("you clicked on "OK"");
Note: In JavaScript, does not have a type to represent a single
character. To represent a single character in JavaScript, we
have to create a string that contain only single character. A
string that contains empty string or zero characters ("") is an
empty or string with zero-length.
String(value) function can be used to convert any value to
string datatype.

Undefined:
Undefined is a variable which doesn’t have any defined value.
Example:
var num; // contains no value
alert(num);// will get undefined

Boolean:
Boolean have two values i.e. “true or false” or 1 or 0 and are
logical representative.
Example:
if(confirm('Are you sure to leave this page')){
//you will be redirected to the following URL if above condition is true
means if someone clicks on the OK button
window.location.href = 'http://www.admecindia.co.in';
}else{
//nothing will happen if someone clicks on CANCEL button as you
will receive false as the result
return false;
}
Note: In above example you either get True or False depends on
the button you clicked means you are getting a Boolean value.

Null:
Null is exactly having single value when Null is defined or
nothing. Null is considered as an object in JavaScript.
var my_value = null;
alert(my_value * 20); //0
Note:
1. null gets converted to the false boolean value and i.e. 0 too
2. null and 'null' both are different terms completely
3. null can be used when you want to reset a variable or want
to store nothing

NOTE
There are 2 other datatypes considered according to
ECMAScript standard.
Symbol: symbol as in primitive datatype which are unique
and unchangeable. In some programming language they are
also called “atoms”.
Object: object data type refers to the structure consist of data
& information for working with the data.

Operators in JavaScript
Types of Operators:
 Assignment Operator: The equal sign (=) is called
“Assignment” Operators.
 Equality Operator: when double the equal sign (==) is
called “Equality” Operator. Is also called comparison
Operator.
 Strict Equality Operators: when Triple the equal sign
(===) is called “Strict Equality” Operator. Is also called
comparison Operator.

Remark
These are just the basics of JavaScript and all
these topics play a vital role when you create
something using JavaScript.
As much you are familiar with these basics more
you would be strong in JavaScript.

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ADMEC MULTIMEDIA
Leader in Animation & Digital Media Education
ISO 9001:2008 CERTIFIED | ADOBE Testing Center
ADMEC MULTIMEDIA INSTITUTE
For More information you can visit :
http://www.admecindia.co.in

Java script basic

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