Javascript tutorial basic for starter

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Javascript Tutorial
Tutorialspoint.com
Javascript is a scripting language produced by Netscape for use within HTML Web
pages.
JavaScript is loosely based on Java and it is built into all the major modern browsers.
This tutorial gives an initial push to start you with Javascript. For more detail kindly
check tutorialspoint.com/javascript

What is JavaScript ?
JavaScript is:







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

JavaScript Syntax:
A JavaScript consists of JavaScript statements that are placed within the <script>... </script>
HTML tags in a web page.
You can place the <script> tag containing your JavaScript anywhere within you web page but it
is preferred way to keep it within the <head> tags.
The <script> tag alert the browser program to begin interpreting all the text between these
tags as a script. So simple syntax of your JavaScript will be 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 segment will look like:

<script language="javascript" type="text/javascript">
JavaScript code
</script>

Your First JavaScript Script:
Let us write our class example to print out "Hello World".

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<html>
<body>
<!-document.write("Hello World!")
//-->
</script>
</body>
</html>
Above code will display following result:

Hello World!

Whitespace and Line Breaks:
JavaScript ignores spaces, tabs, and newlines that appear in JavaScript programs.
Because you can use spaces, tabs, and newlines freely in your program so you are free to
format and indent your programs in a neat and consistent way that makes the code easy to
read and understand.

Semicolons are Optional:
Simple statements in JavaScript are generally followed by a semicolon character, just as they
are in C, C++, and Java. JavaScript, however, allows you to omit this semicolon if your
statements are each placed on a separate line. For example, the following code could be written
without semicolons

<!-var1 = 10
var2 = 20
//-->
</script>
But when formatted in a single line as follows, the semicolons are required:

<!-var1 = 10; var2 = 20;
//-->
</script>
Note: It is a good programming practice to use semicolons.

Case Sensitivity:
JavaScript is a case-sensitive language. This means that language keywords, variables, function
names, and any other identifiers must always be typed with a consistent capitalization of letters.
So identifiers Time, TIme and TIME will have different meanings in JavaScript.
NOTE: Care should be taken while writing your variable and function names in JavaScript.

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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 //-->.

JavaScript Placement in HTML File:
There is a flexibility given to include JavaScript code anywhere in an HTML document. But there
are following most preferred ways to include JavaScript in your HTML file.






Script
Script
Script
Script

in
in
in
in

<head>...</head> section.
<body>...</body> section.
<body>...</body> and <head>...</head> sections.
and external file and then include in <head>...</head> section.

JavaScript DataTypes:
JavaScript allows you to work with three primitive data types:





Numbers eg. 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.

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">
<!-var money;
var name;
//-->
</script>

JavaScript Variable Scope:
The scope of a variable is the region of your program in which it is defined. JavaScript variable
will have only two scopes.

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


Global Variables: A global variable has global scope which means it is defined
everywhere 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.

JavaScript Variable Names:
While naming your variables in JavaScript keep following rules in mind.





You should not use any of the JavaScript reserved keyword as 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 the 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:
The following are reserved words in JavaScript. 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

The Arithmatic Operators:
There are following arithmatic operators supported by JavaScript language:
Assume variable A holds 10 and variable B holds 20 then:
Operator

Description

Example

+

Adds two operands

A + B will give 30

-

Subtracts second operand from the first

A - B will give -10

*

Multiply both operands

A * B will give 200

/

Divide numerator by denumerator

B / A will give 2

%

Modulus Operator and remainder of after an
integer division

B % A will give 0

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++

Increment operator, increases integer value by one A++ will give 11

--

Decrement operator, decreases integer value by
one

A-- will give 9

The Comparison Operators:
There are following comparison operators supported by JavaScript language
Operator

Description

Example

==

Checks if the value of two operands are equal or
not, if yes then condition becomes true.

(A == B) is not true.

!=

Checks if the value of two operands are equal or
not, if values are not equal then condition becomes
true.

(A != B) is true.

>

Checks if the value of left operand is greater than
the value of right operand, if yes then condition
becomes true.

(A > B) is not true.

<

Checks if the value of left operand is less than the
value of right operand, if yes then condition
becomes true.

(A < B) is true.

>=

Checks if the value of left operand is greater than
or equal to the value of right operand, if yes then
condition becomes true.

(A >= B) is not true.

<=

Checks if the value of left operand is less than or
equal to the value of right operand, if yes then
condition becomes true.

(A <= B) is true.

The Logical Operators:
There are following logical operators supported by JavaScript language
Operator

Description

Example

&&

Called Logical AND operator. If both the operands
are non zero then then condition becomes true.

(A && B) is true.

||

Called Logical OR Operator. If any of the two
operands are non zero then then condition
becomes true.

(A || B) is true.

!

Called Logical NOT Operator. Use to reverses the
logical state of its operand. If a condition is true
then Logical NOT operator will make false.

!(A && B) is false.

The Bitwise Operators:
There are following bitwise operators supported by JavaScript language

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Operator

Description

Example

&

Called Bitwise AND operator. It performs a Boolean (A & B) is 2 .
AND operation on each bit of its integer
arguments.

|

Called Bitwise OR Operator. It performs a Boolean
OR operation on each bit of its integer arguments.

(A | B) is 3.

^

Called Bitwise XOR Operator. 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.

(A ^ B) is 1.

~

Called Bitwise NOT Operator. It is a is a unary
operator and operates by reversing all bits in the
operand.

(~B) is -4 .

<<

Called Bitwise Shift Left Operator. It moves all 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 by 2, shifting
two positions is equivalent to multiplying by 4, etc.

(A << 1) is 4.

>>

Called Bitwise Shift Right with Sign Operator. It
(A >> 1) is 1.
moves all bits in its first operand to the right by
the number of places specified in the second
operand. The bits filled in on the left depend on the
sign bit of the original operand, in order to
preserve the sign of the result. If the first operand
is positive, the result has zeros placed in the high
bits; if the first operand is negative, the result has
ones placed in the high bits. Shifting a value right
one place is equivalent to dividing by 2 (discarding
the remainder), shifting right two places is
equivalent to integer division by 4, and so on.

>>>

Called Bitwise Shift Right with Zero Operator. This
operator is just like the >> operator, except that
the bits shifted in on the left are always zero,

(A >>> 1) is 1.

The Assignment Operators:
There are following assignment operators supported by JavaScript language:
Operator

Description

Example

=

Simple assignment operator, Assigns values from
right side operands to left side operand

C = A + B will assigne value of
A + B into C

+=

Add AND assignment operator, It adds right
operand to the left operand and assign the result
to left operand

C += A is equivalent to C = C
+A

-=

Subtract AND assignment operator, It subtracts
right operand from the left operand and assign the
result to left operand

C -= A is equivalent to C = C A

*=

Multiply AND assignment operator, It multiplies

C *= A is equivalent to C = C *

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right operand with the left operand and assign the

A

/=

Divide AND assignment operator, It divides left
operand with the right operand and assign the

C /= A is equivalent to C = C /
A

%=

Modulus AND assignment operator, It takes
modulus using two operands and assign the result
to left operand

C %= A is equivalent to C = C
%A

Miscellaneous Operator
The Conditional Operator (? :)
There is an oprator called conditional operator. This first evaluates an expression for a true or
false value and then execute one of the two given statements depending upon the result of the
evaluation. The conditioanl operator has this syntax:
Operator
?:

Description
Conditional Expression

Example
If Condition is true ? Then value X :
Otherwise value Y

The typeof Operator
The typeof 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.

if statement:
The if statement is the fundamental control statement that allows JavaScript to make decisions
and execute statements conditionally.

Syntax:
if (expression){
Statement(s) to be executed if expression is true
}

if...else statement:
The if...else statement is the next form of control statement that allows JavaScript to execute
statements in more controlled way.

Syntax:
if (expression){
}else{
Statement(s) to be executed if expression is false
}

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if...else if... statement:
The if...else if... statement is the one level advance form of control statement that allows
JavaScript to make correct decision out of several conditions.

Syntax:
if (expression 1){
Statement(s) to be executed
}else if (expression 2){
}else if (expression 3){
}else{
}

if expression 1 is true
if no expression is true

switch statement:
The basic syntax of the 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)
{
case condition 1: statement(s)
break;
case condition 2: statement(s)
break;
...
case condition n: statement(s)
break;
default: statement(s)
}

The while Loop
The most basic loop in JavaScript is the while loop which would be discussed in this tutorial.

Syntax:
while (expression){
}

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.

Syntax:

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do{
Statement(s) to be executed;
} while (expression);

The for Loop
The for loop is the most compact form of looping and 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 the given condition is true or not. If condition is
true then code given inside the loop will be executed otherwise loop will come out.
The iteration statement where you can increase or decrease your counter.

You can put all the three parts in a single line separated by a semicolon.

Syntax:
for (initialization; test condition; iteration statement){
Statement(s) to be executed if test condition is true
}

The for...in Loop
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.

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.

The continue Statement:
The continue statement tells the interpreter to immediately start the next iteration of the loop
and skip remaining code block.
When a continue statement is encountered, program flow will move to the loop check
expression immediately and if condition remain true then it start next iteration otherwise control
comes out of the loop.

Function Definition:
Before we use a function we need to define that function. 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.
The basic syntax is shown here:


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<!-function functionname(parameter-list)
{
statements
}
//-->
</script>

Calling a Function:
To invoke a function somewhere later in the script, you would simple need to write the name of
that function as follows:

<!-sayHello();
//-->
</script>

Exceptions
Exceptions can be handled with the common try/catch/finally block structure.

<!-try {
statementsToTry
} catch ( e ) {
catchStatements
} finally {
finallyStatements
}
//-->
</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 catch block, the exception is placed in e and the catch
block is executed. The finally block executes unconditionally after try/catch.

Alert Dialog Box:
An alert dialog box is mostly used to give a warning message to the users. Like if one input field
requires to enter some text but user does not enter that field then as a part of validation you
can use alert box to give warning message as follows:

<head>
<!-alert("Warning Message");
//-->
</script>
</head>

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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.
You can use confirmation dialog box as follows:

<head>
<!-var retVal = confirm("Do you want to continue ?");
if( retVal == true ){
alert("User wants to continue!");
return true;
}else{
alert("User does not want to continue!");
return false;
}
//-->
</script>
</head>

Prompt Dialog Box:
You can use prompt dialog box as follows:

<head>
<!-var retVal = prompt("Enter your name : ", "your name here");
alert("You have entered : " + retVal );
//-->
</script>
</head>

Page Re-direction
This is very 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:

<head>
<!-window.location="http://www.newlocation.com";
//-->
</script>
</head>

The void Keyword:
The void is an important keyword in JavaScript which can be used as a unary operator that
appears before its single operand, which may be of any type.
This operator specifies an expression to be evaluated without returning a value. Its syntax could
be one of the following:

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<head>
<!-void func()
javascript:void func()
or:
void(func())
javascript:void(func())
//-->
</script>
</head>

The Page Printing:
JavaScript helps you to implement this functionality using print function of window object.
The JavaScript print function window.print() will print the current web page when executed.
You can call this function directly using onclick event as follows:

<head>
<!-//-->
</script>
</head>
<body>
<form>
<input type="button" value="Print" onclick="window.print()" />
</form>
</body>

Storing Cookies:
The simplest way to create a cookie is to assign a string value to the document.cookie object,
which looks like this:

Syntax:
document.cookie = "key1=value1;key2=value2;expires=date";

Reading Cookies:
Reading a cookie is just as simple as writing one, because the value of the document.cookie
object is the cookie. So you can use this string whenever you want to access the cookie.
The document.cookie string will keep a list of name=value pairs separated by semicolons, where
name is the name of a cookie and value is its string value.

JavaScript - Page Redirection
What is page redirection ?

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When you click a URL to reach to a page X but internally you are directed to another page Y that
simply happens because of page re-direction. This concept is different from JavaScript Page
Refresh.
There could be various reasons why you would like to redirect from original page. I'm listing
down few of the reasons:






You did not like the name of your domain and you are moving to a new one. Same time
you want to direct your all visitors to new site. In such case you can maintain your old
domain but put a single page with a page re-direction so that your all old domain
visitors can come to your new domain.
You have build-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 appropriate page.
The Search Engines may have already indexed your pages. But while moving to another
domain then 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
make search engine a fool otherwise this could get your web site banned.

How Page Re-direction works ?
Example 1:
This is very 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:

<head>
<!-window.location="http://www.newlocation.com";
//-->
</script>
</head>
To understand it in better way you can Try it yourself.

Example 2:
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. Following is the simple example to
implement the same:

<head>
<!-function Redirect()
{
window.location="http://www.newlocation.com";
}
document.write("You will be redirected to main page in 10 sec.");
setTimeout('Redirect()', 10000);
//-->
</script>
</head>

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Here setTimeout() is a built-in JavaScript function which can be used to execute another
function after a given time interval.

Example 3:
Following is the example to redirect site visitors on different pages based on their browsers :

<head>
<!-var browsername=navigator.appName;
if( browsername == "Netscape" )
{
window.location="http://www.location.com/ns.htm";
}
else if ( browsername =="Microsoft Internet Explorer")
{
window.location="http://www.location.com/ie.htm";
}
else
{
window.location="http://www.location.com/other.htm";
}
//-->
</script>
</head>

JavaScript - Errors & Exceptions Handling
There are three types of errors in programming: (a) Syntax Errors and (b) Runtime Errors (c)
Logical Errors:

Syntax errors:
Syntax errors, also called parsing errors, occur at compile time for traditional programming
languages and at interpret time for 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 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).

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For example, the following line causes a run time error because here syntax is correct but at run
time it is trying to call a non existed method:

<!-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 can not catch those errors, because it depends on your business requirement what type of
logic you want to put in your program.

The try...catch...finally Statement:
The latest versions of JavaScript added exception handling capabilities. JavaScript implements
the try...catch...finally 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.

Examples:
Here is one example where we are trying to call a non existing function this is causing an
exception raise. Let us see how it behaves without with try...catch:

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<html>
<head>
<!-function myFunc()
{
var a = 100;
alert("Value of variable a is : " + a );
}
//-->
</script>
</head>
<body>
<p>Click the following to see the result:</p>
<form>
<input type="button" value="Click Me" onclick="myFunc();" />
</form>
</body>
</html>
Now let us try to catch this exception using try...catch and display a user friendly message.
You can also suppress this message, if you want to hide this error from a user.

<html>
<head>
{
var a = 100;
try {
} catch ( e ) {
alert("Error: " + e.description );
}
}
//-->
</script>
</head>
<body>
<form>
</form>
</body>
</html>
You can use finally block which will always execute unconditionally after try/catch. Here is an
example:

<html>

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<head>
{
var a = 100;
try {
}catch ( e ) {
alert("Error: " + e.description );
}finally {
alert("Finally block will always execute!" );
}
}
//-->
</script>
</head>
<body>
<form>
</form>
</body>
</html>

The throw Statement:
You can use 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.
Following is the example showing usage of throw statement.

<html>
<head>
{
var a = 100;
var b = 0;
try{
if ( b == 0 ){
throw( "Divide by zero error." );
}else{
var c = a / b;
}
}catch ( e ) {
alert("Error: " + e );
}
}
//-->
</script>
</head>
<body>

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<form>
</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 other function
using try...catch block.

The onerror() Method
The onerror event handler was the first feature to facilitate error handling for JavaScript. The
errorevent is fired on the window object whenever an exception occurs on the page. Example:

<html>
<head>
<!-window.onerror = function () {
alert("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

<html>
<head>
<!-window.onerror = function (msg, url, line) {
alert("Message : " + msg );
alert("url : " + url );
alert("Line number : " + line );
}
//-->

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</script>
</head>
<body>
<form>
</form>
</body>
</html>
You can display extracted information in whatever way you think it is better.
You can use onerror method to show an error message in case there is any problem in loading
an image as follows:

<img src="myimage.gif"
onerror="alert('An error occurred loading the image.')" />
You can use onerror with many HTML tags to display appropriate messages in case of errors.

JavaScript - Form Validation
Form validation used to occur at the server, after the client had entered all necessary data and
then pressed the Submit button. If some of the data that had been entered by the client had
been in the wrong form or was simply missing, the server would have to send all the data back
to the client and request that the form be resubmitted with correct information. This was really
a lengthy process and over burdening server.
JavaScript, provides a way to validate form's data on the client's computer before sending it to
the web server. Form validation generally performs two functions.




Basic Validation - First of all, the form must be checked to make sure data was
entered into each form field that required it. This would need just loop through each
field in the form and check for data.
Data Format Validation - Secondly, the data that is entered must be checked for
correct form and value. This would need to put more logic to test correctness of data.

We will take an example to understand the process of validation. Here is the simple form to
proceed :

<html>
<head>
<title>Form Validation</title>
<!-// Form validation code will come here.
//-->
</script>
</head>
<body>
<form action="/cgi-bin/test.cgi" name="myForm"
onsubmit="return(validate());">
<table cellspacing="2" cellpadding="2" border="1">
<tr>

19 | P a g e

<td align="right">Name</td>
<td><input type="text" name="Name" /></td>
</tr>
<tr>
<td align="right">EMail</td>
<td><input type="text" name="EMail" /></td>
</tr>
<tr>
<td align="right">Zip Code</td>
<td><input type="text" name="Zip" /></td>
</tr>
<tr>
<td align="right">Country</td>
<td>
<select name="Country">
<option value="-1" selected>[choose yours]</option>
<option value="1">USA</option>
<option value="2">UK</option>
<option value="3">INDIA</option>
</select>
</td>
</tr>
<tr>
<td align="right"></td>
<td><input type="submit" value="Submit" /></td>
</tr>
</table>
</form>
</body>
</html>

Basic Form Validation:
First we will show how to do a basic form validation. In the above form we are calling
validate() function to validate data when onsubmit event is occurring. Following is the
implementation of this validate() function:

<!-// Form validation code will come here.
function validate()
{
if( document.myForm.Name.value == "" )
{
alert( "Please provide your name!" );
document.myForm.Name.focus() ;
return false;
}
if( document.myForm.EMail.value == "" )
{
alert( "Please provide your Email!" );
document.myForm.EMail.focus() ;
return false;
}
if( document.myForm.Zip.value == "" ||
isNaN( document.myForm.Zip.value ) ||
document.myForm.Zip.value.length != 5 )
{

20 | P a g e

alert( "Please provide a zip in the format #####." );
document.myForm.Zip.focus() ;
return false;
}
if( document.myForm.Country.value == "-1" )
{
alert( "Please provide your country!" );
return false;
}
return( true );
}
//-->
</script>

Data Format Validation:
Now we will see how we can validate our entered form data before submitting it to the web
server.
This example shows how to validate an entered email address which means email address must
contain at least an @ sign and a dot (.). Also, the @ must not be the first character of the email
address, and the last dot must at least be one character after the @ sign:

<!-function validateEmail()
{
var emailID = document.myForm.EMail.value;
atpos = emailID.indexOf("@");
dotpos = emailID.lastIndexOf(".");
if (atpos < 1 || ( dotpos - atpos < 2 ))
{
alert("Please enter correct email ID")
document.myForm.EMail.focus() ;
return false;
}
return( true );
}
//-->
</script>

Javascript - Browsers Compatibility
It is important to understand the differences between different browsers in order to handle each
in the way it is expected. So it is important to know which browser your Web page is running in.
To get information about the browser your Web page is currently running in, use the built-in
navigator object.

Navigator Properties:

21 | P a g e

There are several Navigator related properties that you can use in your Web page. The following
is a list of the names and descriptions of each:
Property

Description

appCodeName This property is a string that contains the code name of the browser, Netscape
for Netscape and Microsoft Internet Explorer for Internet Explorer.
appVersion

This property is a string that contains the version of the browser as well as
other useful information such as its language and compatibility.

language

This property contains the two-letter abbreviation for the language that is used
by the browser. Netscape only.

mimTypes[]

This property is an array that contains all MIME types supported by the client.
Netscape only.

platform[]

This property is a string that contains the platform for which the browser was
compiled."Win32" for 32-bit Windows operating systems

plugins[]

This property is an array containing all the plug-ins that have been installed on
the client. Netscape only.

userAgent[]

This property is a string that contains the code name and version of the
browser. This value is sent to the originating server to identify the client

Navigator Methods:
There are several Navigator-specific methods. Here is a list of their names and descriptions:
Method

Description

javaEnabled()

This method determines if JavaScript is enabled in the client. If
JavaScript is enabled, this method returns true; otherwise, it returns
false.

plugings.refresh

This method makes newly installed plug-ins available and populates
the plugins array with all new plug-in names. Netscape only.

preference(name,value) This method allows a signed script to get and set some Netscape
preferences. If the second parameter is omitted, this method will
return the value of the specified preference; otherwise, it sets the
value. Netscape only.
taintEnabled()

22 | P a g e

This method returns true if data tainting is enabled and false
otherwise.

Browser Detection:
There is a simple JavaScript which can be used to find out the name of a browser and then
accordingly an HTML page can be served to the user.

<html>
<head>
<title>Browser Detection Example</title>
</head>
<body>
<!-var userAgent
= navigator.userAgent;
var opera
= (userAgent.indexOf('Opera') != -1);
var ie
= (userAgent.indexOf('MSIE') != -1);
var gecko
= (userAgent.indexOf('Gecko') != -1);
var netscape
= (userAgent.indexOf('Mozilla') != -1);
var version
= navigator.appVersion;
if (opera){
document.write("Opera based browser");
// Keep your opera specific URL here.
}else if (gecko){
document.write("Mozilla based browser");
// Keep your gecko specific URL here.
}else if (ie){
document.write("IE based browser");
// Keep your IE specific URL here.
}else if (netscape){
document.write("Netscape based browser");
// Keep your Netscape specific URL here.
}else{
document.write("Unknown browser");
}
// You can include version to along with any above condition.
document.write("<br /> Browser version info : " + version );
//-->
</script>
</body>
</html>

Javascript - The String Object
The String object let's you work with a series of characters and wraps Javascript's string
primitive data type with a number of helper methods.
Because Javascript automatically converts between string primitives and String objects, you can
call any of the helper methods of the String object on a string primitive.

Syntax:
Creating a String object:

var val = new String(string);

23 | P a g e

The string parameter is series of characters that has been properly encoded.

String Properties:
Here is a list of each property and their description.
Property

Description

constructor

Returns a reference to the String function that created the object.

length

Returns the length of the string.

prototype

The prototype property allows you to add properties and methods to an
object.

String Methods
Here is a list of each method and its description.
Method

Description

charAt()

Returns the character at the specified index.

charCodeAt()

Returns a number indicating the Unicode value of the character at the
given index.

concat()

Combines the text of two strings and returns a new string.

indexOf()

Returns the index within the calling String object of the first occurrence of
the specified value, or -1 if not found.

lastIndexOf()

Returns the index within the calling String object of the last occurrence of
the specified value, or -1 if not found.

localeCompare()

Returns a number indicating whether a reference string comes before or
after or is the same as the given string in sort order.

match()

Used to match a regular expression against a string.

replace()

Used to find a match between a regular expression and a string, and to
replace the matched substring with a new substring.

search()

Executes the search for a match between a regular expression and a
specified string.

24 | P a g e

slice()

Extracts a section of a string and returns a new string.

split()

Splits a String object into an array of strings by separating the string into
substrings.

substr()

Returns the characters in a string beginning at the specified location
through the specified number of characters.

substring()

Returns the characters in a string between two indexes into the string.

toLocaleLowerCase() The characters within a string are converted to lower case while
respecting the current locale.
toLocaleUpperCase() The characters within a string are converted to upper case while
respecting the current locale.
toLowerCase()

Returns the calling string value converted to lower case.

toString()

Returns a string representing the specified object.

toUpperCase()

Returns the calling string value converted to uppercase.

valueOf()

Returns the primitive value of the specified object.

String HTML wrappers
Here is a list of each method which returns a copy of the string wrapped inside the appropriate
HTML tag.
Method

Description

anchor()

Creates an HTML anchor that is used as a hypertext target.

big()

Creates a string to be displayed in a big font as if it were in a <big> tag.

blink()

Creates a string to blink as if it were in a <blink> tag.

bold()

Creates a string to be displayed as bold as if it were in a <b> tag.

fixed()

Causes a string to be displayed in fixed-pitch font as if it were in a <tt> tag

fontcolor()

Causes a string to be displayed in the specified color as if it were in a <font
color="color"> tag.

25 | P a g e

fontsize()

Causes a string to be displayed in the specified font size as if it were in a
<font size="size"> tag.

italics()

Causes a string to be italic, as if it were in an <i> tag.

link()

Creates an HTML hypertext link that requests another URL.

small()

Causes a string to be displayed in a small font, as if it were in a <small>
tag.

strike()

Causes a string to be displayed as struck-out text, as if it were in a <strike>
tag.

sub()

Causes a string to be displayed as a subscript, as if it were in a <sub> tag

sup()

Causes a string to be displayed as a superscript, as if it were in a <sup> tag

Javascript - The Arrays Object
The Array object let's you store multiple values in a single variable.

Syntax:
Creating a Array object:

var fruits = new Array( "apple", "orange", "mango" );
The Array parameter is a list of strings or integers. When you specify a single numeric
parameter with the Array constructor, you specify the initial length of the array. The maximum
length allowed for an array is 4,294,967,295.
You can create array by simply assigning values as follows:

var fruits = [ "apple", "orange", "mango" ];
You will use ordinal numbers to access and to set values inside an array as follows:





fruits[0] is the first element
fruits[1] is the second element
fruits[2] is the third element

Array Properties:

26 | P a g e

Property

Description

constructor

Returns a reference to the array function that created the object.

index

The property represents the zero-based index of the match in the string

input

This property is only present in arrays created by regular expression
matches.

length

Reflects the number of elements in an array.

prototype

object.

Array Methods
Method

Description

concat()

Returns a new array comprised of this array joined with other array(s)
and/or value(s).

every()

Returns true if every element in this array satisfies the provided testing
function.

filter()

Creates a new array with all of the elements of this array for which the
provided filtering function returns true.

forEach()

Calls a function for each element in the array.

indexOf()

Returns the first (least) index of an element within the array equal to the
specified value, or -1 if none is found.

join()

Joins all elements of an array into a string.

lastIndexOf()

Returns the last (greatest) index of an element within the array equal to the
specified value, or -1 if none is found.

map()

Creates a new array with the results of calling a provided function on every
element in this array.

pop()

Removes the last element from an array and returns that element.

27 | P a g e

push()

Adds one or more elements to the end of an array and returns the new
length of the array.

reduce()

Apply a function simultaneously against two values of the array (from leftto-right) as to reduce it to a single value.

reduceRight()

Apply a function simultaneously against two values of the array (from rightto-left) as to reduce it to a single value.

reverse()

Reverses the order of the elements of an array -- the first becomes the last,
and the last becomes the first.

shift()

Removes the first element from an array and returns that element.

slice()

Extracts a section of an array and returns a new array.

some()

Returns true if at least one element in this array satisfies the provided
testing function.

toSource()

Represents the source code of an object

sort()

Sorts the elements of an array.

splice()

Adds and/or removes elements from an array.

toString()

Returns a string representing the array and its elements.

unshift()

Adds one or more elements to the front of an array and returns the new
length of the array.

JavaScript - The Date Object
The Date object is a datatype built into the JavaScript language. Date objects are created with
the new Date( ) as shown below.
Once a Date object is created, a number of methods allow you to operate on it. Most methods
simply allow you to get and set the year, month, day, hour, minute, second, and millisecond
fields of the object, using either local time or UTC (universal, or GMT) time.
The ECMAScript standard requires the Date object to be able to represent any date and time, to
millisecond precision, within 100 million days before or after 1/1/1970. This is a range of plus or
minus 273,785 years, so the JavaScript is able to represent date and time till year 275755.

Syntax:
Here are different variant of Date() constructor:

28 | P a g e

new
new
new
new

Date( )
Date(milliseconds)
Date(datestring)
Date(year,month,date[,hour,minute,second,millisecond ])

Note: Paramters in the brackets are always optional
Here is the description of the parameters:







No Argument: With no arguments, the Date( ) constructor creates a Date object set to
the current date and time.
milliseconds: When one numeric argument is passed, it is taken as the internal
numeric representation of the date in milliseconds, as returned by the getTime( )
method. For example, passing the argument 5000 creates a date that represents five
seconds past midnight on 1/1/70.
datestring:When one string argument is passed, it is a string representation of a date,
in the format accepted by the Date.parse( ) method.
7 agruments: To use the last form of constructor given above, Here is the description
of each argument:
1. year: Integer value representing the year. For compatibility (in order to avoid
the Y2K problem), you should always specify the year in full; use 1998, rather
than 98.
2. month: Integer value representing the month, beginning with 0 for January to
11 for December.
3. date: Integer value representing the day of the month.
4. hour: Integer value representing the hour of the day (24-hour scale).
5. minute: Integer value representing the minute segment of a time reading.
6. second: Integer value representing the second segment of a time reading.
7. millisecond: Integer value representing the millisecond segment of a time
reading.

Date Properties:
Property

Description

constructor

Specifies the function that creates an object's prototype.

prototype

object.

Date Methods:
Method

Description

Date()

Returns today's date and time

getDate()

Returns the day of the month for the specified date according to

29 | P a g e

local time.
getDay()

Returns the day of the week for the specified date according to
local time.

getFullYear()

Returns the year of the specified date according to local time.

getHours()

Returns the hour in the specified date according to local time.

getMilliseconds()

Returns the milliseconds in the specified date according to local
time.

getMinutes()

Returns the minutes in the specified date according to local time.

getMonth()

Returns the month in the specified date according to local time.

getSeconds()

Returns the seconds in the specified date according to local time.

getTime()

Returns the numeric value of the specified date as the number of
milliseconds since January 1, 1970, 00:00:00 UTC.

getTimezoneOffset()

Returns the time-zone offset in minutes for the current locale.

getUTCDate()

Returns the day (date) of the month in the specified date
according to universal time.

getUTCDay()

Returns the day of the week in the specified date according to
universal time.

getUTCFullYear()

Returns the year in the specified date according to universal time.

getUTCHours()

Returns the hours in the specified date according to universal
time.

getUTCMilliseconds()

Returns the milliseconds in the specified date according to
universal time.

getUTCMinutes()

Returns the minutes in the specified date according to universal
time.

getUTCMonth()

Returns the month in the specified date according to universal
time.

getUTCSeconds()

Returns the seconds in the specified date according to universal
time.

30 | P a g e

getYear()

Deprecated - Returns the year in the specified date according to
local time. Use getFullYear instead.

setDate()

Sets the day of the month for a specified date according to local
time.

setFullYear()

Sets the full year for a specified date according to local time.

setHours()

Sets the hours for a specified date according to local time.

setMilliseconds()

Sets the milliseconds for a specified date according to local time.

setMinutes()

Sets the minutes for a specified date according to local time.

setMonth()

Sets the month for a specified date according to local time.

setSeconds()

Sets the seconds for a specified date according to local time.

setTime()

Sets the Date object to the time represented by a number of
milliseconds since January 1, 1970, 00:00:00 UTC.

setUTCDate()

Sets the day of the month for a specified date according to
universal time.

setUTCFullYear()

Sets the full year for a specified date according to universal time.

setUTCHours()

Sets the hour for a specified date according to universal time.

setUTCMilliseconds()

Sets the milliseconds for a specified date according to universal
time.

setUTCMinutes()

Sets the minutes for a specified date according to universal time.

setUTCMonth()

Sets the month for a specified date according to universal time.

setUTCSeconds()

Sets the seconds for a specified date according to universal time.

setYear()

Deprecated - Sets the year for a specified date according to local
time. Use setFullYear instead.

toDateString()

Returns the "date" portion of the Date as a human-readable string.

toGMTString()

Deprecated - Converts a date to a string, using the Internet GMT
conventions. Use toUTCString instead.

31 | P a g e

toLocaleDateString()

Returns the "date" portion of the Date as a string, using the
current locale's conventions.

toLocaleFormat()

Converts a date to a string, using a format string.

toLocaleString()

Converts a date to a string, using the current locale's conventions.

toLocaleTimeString()

Returns the "time" portion of the Date as a string, using the
current locale's conventions.

toSource()

Returns a string representing the source for an equivalent Date
object; you can use this value to create a new object.

toString()

Returns a string representing the specified Date object.

toTimeString()

Returns the "time" portion of the Date as a human-readable string.

toUTCString()

Converts a date to a string, using the universal time convention.

valueOf()

Returns the primitive value of a Date object.

Date Static Methods:
In addition to the many instance methods listed previously, the Date object also defines two
static methods. These methods are invoked through the Date( ) constructor itself:
Method

Description

Date.parse( )

Parses a string representation of a date and time and returns the
internal millisecond representation of that date.

Date.UTC( )

Returns the millisecond representation of the specified UTC date
and time.

Javascript - The Math Object
The math object provides you properties and methods for mathematical constants and
functions.
Unlike the other global objects, Math is not a constructor. All properties and methods of Math
are static and can be called by using Math as an object without creating it.
Thus, you refer to the constant pi as Math.PI and you call the sine function as Math.sin(x),
where x is the method's argument.

Syntax:
32 | P a g e

Here is the simple syntax to call properties and methods of Math.

var pi_val = Math.PI;
var sine_val = Math.sin(30);

Math Properties:
Property

Description

E

Euler's constant and the base of natural logarithms, approximately 2.718.

LN2

Natural logarithm of 2, approximately 0.693.

LN10

Natural logarithm of 10, approximately 2.302.

LOG2E

Base 2 logarithm of E, approximately 1.442.

LOG10E

Base 10 logarithm of E, approximately 0.434.

PI

Ratio of the circumference of a circle to its diameter, approximately
3.14159.

SQRT1_2

Square root of 1/2; equivalently, 1 over the square root of 2, approximately
0.707.

SQRT2

Square root of 2, approximately 1.414.

Math Methods
Method

Description

abs()

Returns the absolute value of a number.

acos()

Returns the arccosine (in radians) of a number.

asin()

Returns the arcsine (in radians) of a number.

atan()

Returns the arctangent (in radians) of a number.

atan2()

Returns the arctangent of the quotient of its arguments.

33 | P a g e

ceil()

Returns the smallest integer greater than or equal to a number.

cos()

Returns the cosine of a number.

exp()

Returns EN, where N is the argument, and E is Euler's constant, the base of
the natural logarithm.

floor()

Returns the largest integer less than or equal to a number.

log()

Returns the natural logarithm (base E) of a number.

max()

Returns the largest of zero or more numbers.

min()

Returns the smallest of zero or more numbers.

pow()

Returns base to the exponent power, that is, base exponent.

random()

Returns a pseudo-random number between 0 and 1.

round()

Returns the value of a number rounded to the nearest integer.

sin()

Returns the sine of a number.

sqrt()

Returns the square root of a number.

tan()

Returns the tangent of a number.

toSource()

Returns the string "Math".

Regular Expressions and RegExp Object
A regular expression is an object that describes a pattern of characters.
The JavaScript RegExp class represents regular expressions, and both String and RegExp
define methods that use regular expressions to perform powerful pattern-matching and searchand-replace functions on text.

Syntax:
A regular expression could be defined with the RegExp( ) constructor like this:

var pattern = new RegExp(pattern, attributes);
or simply
var pattern = /pattern/attributes;

34 | P a g e

Here is the description of the parameters:




pattern: A string that specifies the pattern of the regular expression or another regular
expression.
attributes: An optional string containing any of the "g", "i", and "m" attributes that
specify global, case-insensitive, and multiline matches, respectively.

Brackets:
Brackets ([]) have a special meaning when used in the context of regular expressions. They are
used to find a range of characters.
Expression

Description

[...]

Any one character between the brackets.

[^...]

Any one character not between the brackets.

[0-9]

It matches any decimal digit from 0 through 9.

[a-z]

It matches any character from lowercase a through lowercase z.

[A-Z]

It matches any character from uppercase A through uppercase Z.

[a-Z]

It matches any character from lowercase a through uppercase Z.

The ranges shown above are general; you could also use the range [0-3] to match any decimal
digit ranging from 0 through 3, or the range [b-v] to match any lowercase character ranging
from b through v.

Quantifiers:
The frequency or position of bracketed character sequences and single characters can be
denoted by a special character. Each pecial character having a specific connotation. The +, *, ?,
and $ flags all follow a character sequence.
Expression

Description

p+

It matches any string containing at least one p.

p*

It matches any string containing zero or more p's.

p?

It matches any string containing one or more p's.

p{N}

It matches any string containing a sequence of N p's

p{2,3}

It matches any string containing a sequence of two or three p's.

35 | P a g e

p{2, }

It matches any string containing a sequence of at least two p's.

p$

It matches any string with p at the end of it.

^p

It matches any string with p at the beginning of it.

Examples:
Following examples will clear your concepts about matching chracters.
Expression

Description

[^a-zA-Z]

It matches any string not containing any of the characters ranging from a through
z and A through Z.

p.p

It matches any string containing p, followed by any character, in turn followed by
another p.

^.{2}$

It matches any string containing exactly two characters.

<
It matches any string enclosed within <b> and </b>.
b>(.*)</b>
p(hp)*

It matches any string containing a p followed by zero or more instances of the
sequence hp.

Literal characters:
Character

Description

Alphanumeric Itself
0

The NUL character (u0000)

t

Tab (u0009)

n

Newline (u000A)

v

Vertical tab (u000B)

f

Form feed (u000C)

r

Carriage return (u000D)

36 | P a g e

xnn

The Latin character specified by the hexadecimal number nn; for example, x0A
is the same as n

uxxxx

The Unicode character specified by the hexadecimal number xxxx; for example,
u0009 is the same as t

cX

The control character ^X; for example, cJ is equivalent to the newline character
n

Metacharacters
A metacharacter is simply an alphabetical character preceded by a backslash that acts to give
the combination a special meaning.
For instance, you can search for large money sums using the 'd'
/([d]+)000/, Here d will search for any string of numerical character.

metacharacter:

Following is the list of metacharacters which can be used in PERL Style Regular Expressions.

Character
.
s
S
d
D
w
W
[b]
[aeiou]
[^aeiou]
(foo|bar|baz)

Description
a single character
a whitespace character (space, tab, newline)
non-whitespace character
a digit (0-9)
a non-digit
a word character (a-z, A-Z, 0-9, _)
a non-word character
a literal backspace (special case).
matches a single character in the given set
matches a single character outside the given set
matches any of the alternatives specified

Modifiers
Several modifiers are available that can make your work with regexps much easier, like case
sensitivity, searching in multiple lines etc.
Modifier

Description

i

Perform case-insensitive matching.

m

Specifies that if the string has newline or carriage return characters, the ^ and $
operators will now match against a newline boundary, instead of a string boundary

g

Perform a global matchthat is, find all matches rather than stopping after the first
match.

RegExp Properties:

37 | P a g e

Property

Description

constructor

Specifies the function that creates an object's prototype.

global

Specifies if the "g" modifier is set.

ignoreCase

Specifies if the "i" modifier is set.

lastIndex

The index at which to start the next match.

multiline

Specifies if the "m" modifier is set.

source

The text of the pattern.

RegExp Methods:
Method

Description

exec()

Executes a search for a match in its string parameter.

test()

Tests for a match in its string parameter.

toSource()

Returns an object literal representing the specified object; you can use this
value to create a new object.

toString()

Returns a string representing the specified object.

Further Detail:
Refer to the link http://www.tutorialspoint.com/javascript

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Javascript tutorial basic for starter

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Javascript tutorial basic for starter