TUTORIAL 10:
PROGRAMMING WITH
JAVASCRIPT
Session 2: What is JavaScript?
Objectives
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What is JavaScript?
What can JavaScript do?
JavaScript – How to
JavaScript – Where to
Writing JavaScript Statements
Writing JavaScript Comments
Declaring Variables in JavaScript
What is JavaScript?
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JavaScript was designed to add interactivity to
HTML pages
JavaScript is a scripting language
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A scripting language is a lightweight programming
language
JavaScript is an interpreted language (means that
scripts execute without preliminary compilation)
Everyone can use JavaScript without purchasing a
license
What can JavaScript do?
JavaScript gives HTML designers a programming tool
 JavaScript can read and write HTML elements
 JavaScript can react to events
 JavaScript can change HTML content
 JavaScript can change HTML images
 JavaScript can change HTML styles
 JavaScript can be used to validate data
Example of JavaScript Use
Other Examples of JavaScript Uses
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http://grhainfo.org/codingbootcamp2/registration.
htm
http://www.gcsu.edu
JavaScript – How to..
A JavaScript program can be placed directly in an
HTML file or it can be saved in an external text file
 Insert a client-side script in a Web page when using
the script element
<script type="text/javascript">
script commands
</script>
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JavaScript: Script Element
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In Class Example
 Writing
to the HTML document
 Changing HTML elements
JavaScript – Where to..
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JavaScript can be put in the <body> and in the
<head> sections of an HTML page.
JavaScript can be embedded in the HTML code.
JavaScript can also be placed in external files.
JavaScript: in head, body, and
external
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In Class Examples
 In
body
 In head
 External JavaScript file
JavaScript Statements
JavaScript is a sequence of statements to be
executed by the browser.
 JavaScript is case-sensitive.
 A JavaScript statement is a command to a browser.
The purpose of the command is to tell the browser
what to do.
 Example:
document.write("Hello Dolly");
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JavaScript Statements
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In Class Examples
 JavaScript
Code
 JavaScript Code Block (use of a function)
JavaScript Comments
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Commenting your code is an important
programming practice
// comment text for a single line
/* comment text for multiple lines
JavaScript Comments
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In-Class Example:
 Add
a single-line comment
 Add a multi-line comment
JavaScript Variables
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As with algebra, JavaScript variables are used to
hold values or expressions.
A variable can have a short name, like x, or a
more descriptive name, like carname.
Rules for JavaScript variable names:
 Variable
names are case sensitive (y and Y are two
different variables)
 Variable names must begin with a letter, the $
character, or the underscore character
Declaring JavaScript Variables
Declaring a variable tells the JavaScript to reserve
memory space for the variable.
 To declare a JavaScript variable, use the statement
var variable;
where variable is the name assigned to the variable.
 To declare a JavaScript variable and set its initial
value, use
var variable = value;
where value is the initial value of the variable.
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Declaring JavaScript Variables
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JavaScript data types:
 Numeric
values
 Text strings
 Boolean values
 Null values
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You must declare a variable before using it.
Declaring JavaScript Variables
Numeric value is any number, such as 13, 22.5,
-3.14159 etc.
 Text string is any group of text characters, such as
“Hello” or “Happy Holidays!”
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 Must
be enclosed within either double or single
quotations (but not both)
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Boolean values accept only true and false values
Null value has no value at all
Declaring Variables
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In Class Example