Introduction to JavaScript.pptx

01.01 Introduction
Introduction to JavaScript

01.01 Introduction
Welcome
• JavaScript has many uses, but we will
focus on Web Design, specifically how to
add interactivity
• In this class there is an assumption that
you are new to programming, but you
know HTML and CSS

01.01 Introduction
JavaScript and Client-Side Scripting
JavaScript is a client-side scripting language that
allows Web page authors to develop interactive Web
pages and sites.
Client-side scripting refers to a scripting language that
runs on a local browser (on the client tier) instead of on
a Web server (on the processing tier). Originally
designed for use in Navigator Web browsers,
JavaScript is now also used in most other Web
browsers, including Firefox and Internet Explorer.

01.01 Introduction
Cont..
JavaScript was originally developed as LiveScript by
Netscape in the mid 1990s. It was later renamed to
JavaScript in 1995, and became an ECMA standard in
1997. Now JavaScript is the standard client-side
scripting language for web-based applications, and it is
supported by virtually all web browsers available today,
such as Google Chrome, Mozilla Firefox, Apple Safari,
etc.

01.01 Introduction
Understanding Server-Side Scripting
Server-side scripting refers to a scripting language that
is executed from a Web server. Some of the more
popular server-side scripting languages are PHP, Active
Server Pages (ASP), and Java Server Pages
(JSP). One of the primary reasons for using a server-
side scripting language is to develop interactive Web
sites that communicate with a database.

01.01 Introduction
Conti..
Server-side scripting languages work in the processing
tier and have the ability to handle communication
between the client tier and the data storage tier. At the
processing tier, a server-side scripting language usually
prepares and processes the data in some way before
submitting it to the data storage tier.

01.01 Introduction
Adding JavaScript to Your Web Pages
Using the <script> Element
JavaScript programs run from within a Web page (either
an HTML or XHTML document). That is, you type the
code directly into the Web page code as a separate
section. JavaScript programs contained within
a Web page are often referred to as scripts. Th e
<script> element tells the Web browser that the scripting
engine must interpret the commands it contains.

01.01 Introduction
Conti..
The type attribute of the <script> element tells the
browser which scripting language and which version of
the scripting language is being used. You assign a value
of “text/javascript” to the type attribute to indicate that
the script is written with JavaScript.
<script type="text/javascript">
statements
</script>

01.01 Introduction
Embedding the JavaScript Code
You can embed the JavaScript code directly within your
web pages by placing it between the <script> and
</script> tags. Here's an example:
<body>
<script>
var salaan = "Hello World!";
document.write(salaan); // Prints: Hello World!
</script>
</body>

01.01 Introduction
Calling an External JavaScript File
You can also place your JavaScript code into a separate
file with a .js extension, and then call that file in your
document through the src attribute of the <script> tag,
like this:
<script src="js/hello.js"></script>
This is useful if you want the same scripts available to
multiple documents. It saves you from repeating the
same task over and over again, and makes your website
much easier to maintain.

01.01 Introduction
Conti..
Example
// A function to display a message
function sayHello() {
alert("Hello World!");
}
// Call function on click of the button
document.getElementById("myBtn").onclick = sayHello;

01.01 Introduction
Conti..
Example
html>
<head>
<title>Including External JavaScript File</title>
</head>
<body>
<button type="button" id="myBtn">Click Me</button>
<script src="hello.js"></script>
</body>
</html>

01.01 Introduction
Placing the JavaScript Code Inline
You can also place JavaScript code inline by inserting it
directly inside the HTML tag using the special tag
attributes such as onclick, onmouseover, onkeypress,
onload, etc.
<body>
<button onclick="alert('Hello World!')">Click
Me</button>
</body>

01.01 Introduction
Case Sensitivity in JavaScript
JavaScript is case-sensitive. This means that variables,
language keywords, function names, and other
identifiers must always be typed with a consistent
capitalization of letters.
For example, the variable myVar must be typed myVar
not MyVar or myvar. Similarly, the method name
getElementById() must be typed with the exact case not
as getElementByID().

01.01 Introduction
Adding Comments to a JavaScript
Comments are nonprinting lines that
you place in your code to contain various types of
remarks, including the name of the program, your name
and the date you created the program, or instructions to
future programmers who may need to modify your work.
JavaScript support single-line as well as multi-line
comments. Single-line comments begin with a double
forward slash (//).Whereas, a multi-line comment begins
with a slash and an asterisk (/*) and ends with an asterisk
and slash (*/).

01.01 Introduction
Conti...
Example of Single Comment
// This is my first JavaScript program
document.write("Hello World!");
Example of Multi-line Comment
/* This is my first program
in JavaScript */
document.write("Hello World!");

01.01 Introduction
Variables
The values a program stores in computer memory are
commonly called variables. The data or value stored in the
variables can be set, updated, and retrieved whenever
needed. You can create or declare JavaScript a variable
using 3 keywords that are var, let, and const, whereas the
assignment operator (=) is used to assign value to a
variable, like this: var varName = value;

01.01 Introduction
Conti…
var keyword: The var is the oldest keyword to declare a
variable in JavaScript.
<script>
var a = 10;
Console.log(a);
</script>

01.01 Introduction
Conti…
let keyword: The let keyword is an improved version of the
var keyword.
<script>
<script>
let a = 10;
let b = 9
console.log(b);
console.log(a);
</script>

01.01 Introduction
Conti…
const keyword: The const keyword has all the properties
that are the same as the let keyword, except the user
cannot update it.
<script>
const a = 10;
a = 9
console.log(a)
</script>

01.01 Introduction
Conti…
var let const
The scope of a var variable
is functional scope.
The scope of a let variable
is block scope.
The scope of
a const variable is block
scope.
It can be updated and re-
declared into the scope.
It can be updated but
cannot be re-declared into
the scope.
It cannot be updated or re-
declared into the scope.
It can be declared without
initialization.
It can be declared without
initialization.
It cannot be declared
without initialization.

01.01 Introduction
Cont..
Example
var name = "Peter Parker";
var age = 21;
var isMarried = false;
// Displaying a variable value
var x = 10;
var y = 20;
var sum = x + y;
alert(sum); // Outputs: 30

INTERACTIVITY
WITH JAVASCRIPT
01.01 Introduction
Naming Conventions for JavaScript Variables
These are the following rules for naming a JavaScript
variable:
• A variable name must start with a letter, underscore (_),
or dollar sign ($).
• A variable name cannot start with a number.
• A variable name can only contain alpha-numeric
characters (A-z, 0-9) and underscores.
• A variable name cannot contain spaces.
• A variable name cannot be a JavaScript keyword or a
JavaScript reserved word.

Introduction to JavaScript.pptx

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