Maharashtra Board Class 12 Information Technology Chapter 3 Advanced Javascript PDF Download

Advanced Javascript

Let Us Learn

Features of JavaScript, difference between client side scripting and server side scripting.

Looping structures.

DOM Objects and window object in JavaScript.

Inbuilt objects such String, Math, Array, Date and Number with its properties and Methods.

Simple JavaScript programs to do validations and user interaction.

Introduction

There is variety of scripting languages used to develop dynamic websites. JavaScript is an interpreted scripting language. An interpreted language is a type of programming language that executes its instructions directly and freely without compiling machine language instructions in precious program. Program is a set of instructions used to produce various kinds of outputs. JavaScript was initially created to "make webpages alive". The programs in this language are called scripts.

Features Of JavaScript

JavaScript is light weight scripting language because it does not support all features of object oriented programming languages.

No need of special software to run JavaScript programs.

JavaScript is object oriented scripting language and it supports event based programming facility. It is case sensitive language.

JavaScript helps the browser to perform input validation without wasting the user's time by the Web server access.

It can handle date and time very effectively.

Most of the JavaScript control statements syntax is same as syntax of control statements in other programming languages.

An important part of JavaScript is the ability to create new functions within scripts. Declare a function in JavaScript using function keyword.

Software that can run on any hardware platform (PC, Mac, SunSparc etc.) or software platform (Windows, Linux, Mac OS etc.) is called as platform independent software. JavaScript is platform independent scripting language. Any JavaScript-enabled browser can understand and interpreted JavaScript code. Due to different features, JavaScript is known as universal client side scripting language.

Teacher's Note

JavaScript is like a magic helper for websites. Just like you write instructions to make a toy robot work, JavaScript writes instructions to make websites do things when you click buttons.

Exam Trick

Remember: JavaScript = Client Side = Browser. Server Side = Web Server. Think: "Java = Java-Script, runs in the script of your browser!"

Points to Remember

JavaScript is lightweight and does not need special software to run.

It is platform independent language that works on any browser.

JavaScript is case sensitive which means A and a are different.

It can do input validation without troubling the web server.

JavaScript can handle dates and times very well.

There Are Two Types Of Scripting

Server side scripting and Client side scripting.

Client-Side Scripting

In this type, the script resides on client computer (browser) and that can run on the client. Basically, these types of scripts are placed inside an HTML document.

Server-Side Scripting

In this type, the script resides on web server. To execute the script it must be activated by client then it is executed on web server.

Difference Between Server Side Scripting And Client Side Scripting

1. Server-side scripting is used at the backend, where the source code is not visible or hidden at the client side (browser). On the other hand, client-side scripting is used at the frontend which users can see from the browser. So Server-side scripting is more secure than client-side scripting.

2. When a server-side script is processed it communicates to the server. As against, client-side scripting does not need any server interaction.

3. The client-side scripting language involves languages such as HTML5, JavaScript etc. In contrast, programming languages such as PHP, ASP.net, Ruby, ColdFusion, Python, C# etc. are server side scripting languages.

4. Server-side scripting is useful in customizing the web pages and implements the dynamic changes in the websites. Conversely, the client-side scripts are generally used for validation purpose and effectively minimize the load to the server.

5. Special software (web server software) is required to execute server-side script, whereas client side scripts requires web browser as an interface.

Do You Know?

There are some popular framework / libraries.

Angular JS: It is a java script based open source frontend web framework devloped mainly for single page application.

Vue JS: It is javascript based frame work for building interactive user interface (UI). It can be easly integrated with other projects and libraries.

React: It consists of javascript libraries for building UI for single page application and mobile application.

Teacher's Note

Client-side script runs on your computer like a fast game. Server-side script is like asking your teacher a question - it takes time to go to school and come back with answer.

Exam Trick

Remember: Client Side = Fast and Secure in browser. Server Side = Slow but more powerful. Like: Playing a game offline (client) vs online (server).

Points to Remember

Client-side scripting runs on the user's browser and is fast.

Server-side scripting runs on the web server and is more secure.

JavaScript is a client-side language while PHP is a server-side language.

Client-side scripting is good for validation and does not waste server power.

Server-side scripting is hidden from users and more powerful.

Switch Case And Looping Structures

Previous year we have learnt different basic syntax of javascript such as variable declaration, if structure, function etc. Let us learn some extra features:

Switch Case Statement

JavaScript has a built–in multiway decision statement known as Switch. The switch statement test the value of given expression against a list of case values and when match is found, a block of statement associated with that case is executed. There should not be duplicity between the cases. The value for the case must be similar data type as the variable in switch. The default statement is not mandatory.

Syntax

switch(expression)

{

case value1:

statement block 1;

break;

case value2:

statement block 2;

break;

…………......

case value n:

statement block n;

break;

default:

statement block ;

}

Program

<!DOCTYPE html>

<head><title>Javascript Program</title></head>

<body>

<h1> use of switch case </h1>

<script type="text/javascript">

var day=6;

switch(day)

{

case 1: alert("Monday"); break;

case 2: alert("Tuesday"); break;

case 3: alert("Wednesday"); break;

case 4:alert("Thursday"); break;

case 5: alert("Friday"); break;

case 6: alert("Saturday"); break;

case 7: alert("Sunday"); break;

default: alert("Invalid day");

}

</script></body></html>

Output

Saturday

Note

'language' attribute of <Script> is replaced by 'type' attribute in all the programs as it is standardised.

Teacher's Note

Switch case is like choosing a menu item in a restaurant. If you say "chicken", you get chicken. If you say "pizza", you get pizza. It matches your choice to the right food.

Exam Trick

Remember: Switch = many if-else. Break = stop here. Default = if nothing matches, do this. Like: Switch the TV channel to the one you want!

Points to Remember

Switch statement is used when you have many choices.

Break statement stops the switch from checking more cases.

Default case runs if no other case matches.

Case values must be the same data type as the switch expression.

The default statement is optional in switch.

Looping Statement

While creating programming logic, we need to execute some statements repeatedly. Iteration refers to the execution of statement or a group of statements of code for a fixed number of times or till the condition is satisfied. The condition should be boolean condition. Some commonly used JavaScript looping statements are:

1. For…….Loop

This loop executes statements as long as condition becomes true, control comes out from the loop when condition becomes false. Benefit of for-loop is that it combines initialization, condition and loop iteration (increment or decrement) in single statement.

Syntax

for(initialization;condition;iteration)

{

statement block;

}

Initialization is assigning initial value to the variable, which executes only once, and then the condition is checked. Loop will execute statements in statement block till the condition is true. When condition becomes false control is transferred out of the loop and it will execute remaining program. Iteration means increment or decrement value of a running variable.

Example

for(i=1;i<=5;i++)

{

document.writeln(i);

}

for(i=5;i>=1;i--)

{

document.writeln(i);

}

Output

1

2

3

4

5

Output

5

4

3

2

1

2. While…..Loop

This loop executes statements as long as the condition is true. As soon as condition becomes false control comes out of the loop.

Syntax

initialization;

while(condition)

{

statement block;

}

The statement within the loop may be a single line or a block of statements. If the statement within loop is a single line then the curly parenthesis is optional. Here loop will be executed repeatedly as long as the condition is true. Note that if condition always true then loop would be executed infinitely so after some execution condition becomes false.

Example

var i=1

while(i<=5)

{

document.writeln(i);

i=i+1;

}

Program For Loop

<!DOCTYPE html>

<head><title>Table-I</title>

<script type="text/javascript">

function display()

{

var i,a;

a=form1.t1.value

for(i=1;i<=10;i++)

{

document.write(a*i + "<br/>");

}

}

</script></head>

<body>

<form name="form1">

Enter number to display table:-

<input type="text" name="t1">

<input type="button" value=" Display Table" onClick="display()">

</body>

</html>

Teacher's Note

For loop is like running around a playground 5 times. While loop is like running until you feel tired. Both do things many times but in different ways.

Exam Trick

Remember: For = count (1 to 10). While = condition (keep going until tired). For is faster when you know how many times. While is for unknown number of times.

Points to Remember

For loop is used when you know exactly how many times to repeat.

While loop is used when you do not know how many times to repeat.

Both loops can be stopped using the break statement.

Initialization happens only once at the start of for loop.

The condition must become false eventually or loop runs forever.

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