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TUTORIAL 10: PROGRAMMING WITH JAVASCRIPT
Session 2: What is JavaScript?
Objectives
What is JavaScript? What can JavaScript do? JavaScript – How to Writing JavaScript Statements JavaScript – Where to Writing JavaScript Comments Declaring Variables in JavaScript
What is JavaScript?
JavaScript was designed to add interactivity to HTML pages
JavaScript is a scripting language 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 http://grhainfo.org/codingbootcamp2/reg
istration.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>
JavaScript: Script Element In Class Example
Writing to the HTML document Changing HTML elements
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");
JavaScript Statements
In Class Examples JavaScript Code JavaScript Code Block (use of a
function)
JavaScript – Where to..
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 In Class Examples
In body In head External JavaScript file
JavaScript Comments
Commenting your code is an important programming practice
// comment text for a single line
/* comment text for multiple lines
JavaScript Comments
In-Class Example: Add a single-line comment Add a multi-line comment
JavaScript Variables
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
statementvar variable;where variable is the name assigned to the
variable. To declare a JavaScript variable and set its
initial value, usevar variable = value;where value is the initial value of the variable.
Declaring JavaScript Variables JavaScript data types:
Numeric values Text strings Boolean values Null values
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!” Must be enclosed within either double or single
quotations (but not both) Boolean values accept only true and false
values Null value has no value at all
Declaring Variables
In Class Example
