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Session 2: What is JavaScript?Tutorial 10: Programming
with javascript
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What is JavaScript?•
What can JavaScript do?•
JavaScript – How to•
Writing JavaScript Statements•
JavaScript – Where to•
Writing JavaScript Comments•
Declaring Variables in JavaScriptObjectives
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JavaScript was designed to add interactivity to HTML pages•
JavaScript is a scripting language– A scripting language is a lightweight programming language
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JavaScript is an interpreted language (means that scripts execute without preliminary compilation)•
Everyone can use JavaScript without purchasing a licenseWhat is JavaScript?
JavaScript gives HTML designers a programming tool
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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 dataWhat can JavaScript do?
Example of JavaScript
Use
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http://grhainfo.org/codingbootcamp2/regist ration.htm•
http://www.gcsu.eduOther Examples of
JavaScript Uses
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A JavaScript program can be placed directly in an HTML file or it can be saved in anexternal text file
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Insert a client-side script in a Web page when using the script element<script type="text/javascript">
script commands
</script>
JavaScript – How to..
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In Class Example– Writing to the HTML document – Changing HTML elements
JavaScript: Script
Element
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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
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In Class Examples– JavaScript Code
– JavaScript Code Block (use of a function)
JavaScript Statements
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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 – Where to..
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In Class Examples– In body – In head
– External JavaScript file
JavaScript: in head,
body, and external
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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 Comments
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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
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.
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
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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)
