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:Web
Browser
Web
Server
1 - Request an HTML Page
4 - Present HTML Content
2 - Retrieve requested HTML
3 - Return HTML to Browser
HTML
How it Works
I n t e r n e t
Client requests page
Completed HTML sent to client
Web Server
Client Machine With Web Browser
• The script, written by the website developer, generates the HTML code of the page requested.
• The HTML code is not actually a file. The code is actually held in the server’s memory until it is sent directly to the client.
• A script may run other scripts, depending on its function. It will however still only give one end result.
• A website does not have to be completely made up of either scripts or HTML files. It can use a combination of the two.
Script builds
HTML code
HTML ready to send
Server runs script
[ ASP / PHP / Ruby ]Script
HTML Code
How Scripting Languages Work
What Are Scripts?
A new style of programming language different from system programming languages
It does not matter what scripting language a website uses because there are no compatibility issues with clients’ web browsers.
Designed as glue language or system integration language
A single statement can execute huge number of machine instructions
Can create dynamic web pages
Change based on user input
The client only ever sees the final HTML generated by the script and not the script itself.
Scripts often finish running in several milliseconds. Most web servers can run many scripts simultaneously with a minimal performance hit.
Two Types
Server-side Scripting Language
Can use huge resources of the server
Complete all processing in the server and send plain pages to the client
Reduces client-side computation overhead
Client-side Scripting Language
Does not involve server processing
Complete application is downloaded to the client browser
Client browser executes it locally
Are normally used to add functionality to web pages e.g. different menu styles, graphic displays or dynamic advertisements
I n t e r n e t
1. Client requests page
2. Web server sends the HTML file to the client
Web ServerClient Machine
With Web Browser
• A simple website is made up of one or more static HTML files. This means the page
content does not change.
• The only way to update a page is for the author to edit the file.
• This is fine for small websites or those that require little updating.
• Static pages will not work for websites that need to deliver lots of custom and up-to-
date content: e-commerce, auctions, blogs, search engines, online banking
Static Web Pages
• The facebook homepage could be considered static because it has a fixed layout and content. It does not change.
• After Login results page however is dynamic. This means its content can be changed.
• The only practical way to create this page is by using a script
• The user never sees the work a script does, only the end result it sends back to their browser.
Dynam
ic W
ebPage
Sta
tic W
ebPage
Dynamic Web Pages
Perl, Python, Ruby Perl
Found on all Windows and Linux servers
Can handle text manipulation tasks
Excellent web scripting language
high-traffic websites that use Perl extensively
include Priceline.com, Craigs List, IMDB
Python
Can be used as a script or a programming language
OOP language with a lot of features which support of web applications as well as software programs
Industrial Light & Magic: "The Phantom Menace", "The Mummy Returns"
Walt Disney Feature Animation: uses scripts in their animation production system.
Shopzilla: configuration management and deployment, automated testing and internal tool development.
Perl Python, Ruby
Ruby
Various blogs, data processing applications
Twitter, Shopify, Groupon, HUlu
Ruby, Perl, Python, etc., are all open source
Rely on volunteers to
Write documentation
Write test cases
Maintain the systems
Port to new platforms
Fix bugs
Implement libraries
Implement new features
ASP-PHP
Active Server Pages (ASP)
Server side scripting language
Developed by Microsoft
Good at connecting to Microsoft databases
Runs only on Microsoft servers
Microsoft.com, GoDaddy, Skype, NYTimes.com
PHP (Hypertext Pre-Processor)
Especially good at connecting to MySQL
Generate Dynamic content and good User Interface
Server side execution
Facebook, Wikipedia, Yahoo, Photo-bucket, &
WordPress
JavaScript
JavaScript
Java and JavaScript are two completely different languages in both concept and design
Client-side & server-side scripting language
Enhance dynamics and interactive features of a web page
Allows one to perform calculations, write interactive games, add special effects, customize graphic selections, create security passwords
used in millions of web pages
to improve the design
to validate forms
to detect browsers
to create cookies
JavaScript and HTML page
<html>
<body>
<script type=“text/javascript”>
document.write(“Hello World!”);
</script>
</body>
</html>
This code produce the output on an HTML page:Hello World!
Tells where the JavaScript ends
Tells where the JavaScript starts
Commands for writing output to a page
Conclusion
Scripting languages make the web development work
Easier
Faster
Best utilization of resources
http://www.w3schools.com/html/html_scripts.asp