Introduction to JavaScript Programming

Introduction to JavaScript
Programming
www.collaborationtech.co.in
Bengaluru INDIA
Presentation By
Ramananda M.S Rao

Introduction to JavaScript Basics
Content
What is JavaScript ?
Where JavaScript is used?
JavaScript Frameworks
Writing JavaScript Code
Using External JavaScript File
Benefits of using External Files
JavaScript Variables
JavaScript Operators
Arrays
Control Structures
Using JavaScript in HTML code
About Us

What is JavaScript?
 Interpreted programming or scripting language from Netscape.
 Easier to code than the compiled languages like C and C++.
 Lightweight and most commonly used script in web pages.
 Allow client-side user to interact and create dynamic pages.
 Cross-platform and object-oriented scripting language.
 Most popular programming language in the world.
 High level, dynamic and untyped programming language.
 Standardized in the ECMAScript language specification.
 Used for shorter programs
 Takes longer time to process than compiled languages.

Where JavaScript is used ?
 When a user requests an HTML page with JavaScript in it, the script is
sent to the browser.
 JavaScript used for creating dynamic web pages.
 The JavaScript language is a free, client-side scripting language
 Scripting adds interactivity to Hypertext Markup Language (HTML)
pages.
 Client-side means that the JavaScript language runs in the browser and
is not used on the server side.
 Client-side scripting allows user interactivity with a web page after the
web page is served by the server and loaded by the browser.
 Used in Web Forms Validations.
 Used in Web and Mobile Development
 Used to create Windows desktop applications
 Used to create cross-platform applications via frameworks.
 Used for Inserting and swapping Contents in Web Pages
 Used across various platforms and browsers

Writing JavaScript Code
The script tags and type attribute are required to include
JavaScript code in an HTML file
<head>
<script type="text/javascript">
/*Example statement here */
// hello world
</script>
</head>

Using External JavaScript File
<script type="text/javascript">
</script>
Use comments to hide JavaScript code from browsers that do not
support it
<script type="text/javascript" src=“js/javascript.js">
</script>

Benefits of using External Files
 External JavaScript files are the most common way to include JavaScript code for
a number of practical reasons
 Search engines can crawl and index web site faster if there is less code within
HTML page.
 Keeping your JavaScript code separate from HTML is cleaner and ultimately
easier to manage.
 On Including multiple JavaScript files in HTML code we can separate the
JavaScript files into different folder structures on web server.
 Clean, organized code is always key to easily managing your website.

JavaScript Variables
There are two types of variables: local and global. You declare local variables
using the var keyword and global variables without using the var keyword.
With the var keyword the variable is considered local because it cannot be
accessed anywhere outside the scope of the place you declare it. For
example, declaring a local variable inside a function, it cannot be accessed
outside of that function, which makes it local to that function.
Declaring the same variable without the var keyword, it is accessible
throughout the entire script, not only within that function. Which makes it
global within script tag.
Declaring a local variable
var num = 10;
To access the value of the num variable at another point in the script, you
simply reference the variable by name Ex:
document.write("The value of num is: "+ num);

JavaScript Operators
I. You need operators when performing any operation in the
JavaScript language. Operations include addition,
subtraction, comparison, and so on. There are four types of
operators in the JavaScript language.
II. Arithmetic
III. Assignment
IV. Comparison
V. Logical

Logical operators
 Logical operators are generally used in conditional statements to
combine comparison operators.
 list describes all the logical operators available in the JavaScript
language.
Logical operators
 Operator Description
 && AND
 || OR
 ! NOT

Arrays
 Arrays are similar to variables, but they can hold multiple values.
 There is no limit to the amount or type of data that you can store in a
JavaScript array
 We can access any value of any item in an array at any time after
declaring it.
 Arrays can hold any data type in the JavaScript language.
 Arrays can store only similar data in any one array.
Storing similar values in an array
var colors = new Array("orange", "blue", "red", "brown");
var shapes = new Array("circle", "square", "triangle", "pentagon");
Accessing values in an array is easy, but there is a catch. Arrays always start
with an ID of 0, rather than 1.
To access an array item you must use its ID, which refers to the item's
position in the array

Storing similar values in an array
var colors = new Array("orange", "blue", "red", "brown");
document.write("Orange: "+ colors[0]);
document.write("Blue: "+ colors[1]);
document.write("Red: "+ colors[2]);
document.write("Brown: "+ colors[3]);
It is also possible to assign a value to a position in an array or update an
item's value in an array, just as you accessed an item in an array
Assigning values to specific positions in an array
var colors = new Array();
colors[0] = "orange"; colors[1] = "blue";
colors[2] = "red"; colors[3] = "brown";
document.write("Blue: "+ colors[1]);
// Update blue to purple
colors[1] = "purple";
document.write("Purple: "+ colors[1]);

Control Structures
Conditional statements
 Conditional statements are the backbone for creating any type of logic
in a scripting or programming language, and the JavaScript language is
no exception.
 Conditional statements determine what action to take based on the
conditions you script. There are four ways to write conditional
statements in the JavaScript language, which are described in Table
Conditional statements Statement
If -Used to execute a script if a specific condition is true
if...else -Used to execute one script if a specific condition is true or another
script if the condition is false
if...else if...else -Used to execute one script if one of unlimited conditions is
true or another script if all conditions are false
Switch- Used to execute one of many scripts
A>B ? document.write(‘a’): document.write(‘b’)

Functions
 Functions are containers for script that is only to be executed by an
event or a call to the function.
 Functions do not execute when the browser initially loads and
executes the script that is included in a web page.
 The purpose of a function is to contain script that has a task so that
you then have the ability to execute that script and run that task at
any time.
Structuring a simple function
var num = 10;
function changeVariableValue()
{ num = 11; }
changeVariableValue();
document.write("num is: "+ num);

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Introduction to JavaScript Programming

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