Tutorial 10: Programming with javascript
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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 JavaScript – Where to Writing JavaScript Statements 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/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> JavaScript: Script Element In Class Example Writing to the HTML document Changing HTML elements 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 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 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 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 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
