SERVER web page repository WEB PAGE instructions stores information and instructions BROWSER retrieves web page and follows instructions Server Web Server Pages Client Browser 1 3 2

 Browser-based language for creating dynamic pages  Functions › simple programming tool › dynamic text › react to events › read and write HTML elements › validate data › detect the browser › create cookies  Significant differences between browsers › More than HTML and CSS › Why no such problems with PHP?  w3schools

HTML Content CSS Presentation JavaScript Behavior

JavaScript Writes Text { document.write (‘ Hello World! '); }

My Page My Page <a href="myfile.html" onMouseover="window.alert('Hello');"> My Page

 JavaScript is very good at processing user input in the web browser  HTML elements receive input  Forms and form elements have unique names › Each unique element can be identified

Name: Phone:

General structure: document.formname.elementname.value Specifically: document.addressform.yourname.value

Personalising an alert box Enter your name:

 When there is too much to do, put it in a separate location  Two options › In the section › In a separate.js file

 A chunk of code that you can imbed in an existing environment  Differences › Resides: desktop or web › Embedding: any page or application or limited › Runs: your machine or server  Let’s add some to a web page

 Resources › ›  Let’s add some to a web page

 Send me an  Reference Reference  Danger: spam

 Customizable homepage of gadgets › Gadgets = widgets › Specific to iGoogle  If it has what you want…

 Visible aggregation: access to multiple web sites or functions  Collection of individual pieces  Tools exist but often “roll your own”

 Aggregation of information presented cohesively  Dynamic information  Should not be able to tell that it is a mashup! 