Week 4 Lesson 9 Fundamentals of Scripting Fundamentals of Scripting Languages Introduction Characteristics Uses Scripting language constructs Assignment 2 Scripting Languages What a scripting language is ID: 592121
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Slide1
Unit 20 - Client Side Customisation of Web Pages
Week 4 – Lesson 9
Fundamentals of ScriptingSlide2
Fundamentals of Scripting Languages
Introduction
Characteristics
Uses
Scripting language constructsSlide3
Assignment 2 - Scripting Languages
What a scripting language is
How it works
What types are available
The main features
How does a scripting language improve functionality
Explain in detail how a browser implements a scripting languageSlide4
Results
22 submissions, 4 missed
7 passes
5 merits
3 distinctions
15 referralsSlide5
P2 Definitions (10)
10 topics to describe
Some missing altogether
Some incomplete –do you proof-read?
“…is shown in the image below.”Slide6
P2 Definitions (10)
Should be original
From a relevant source
quoted
eg
.
“scripting
languages are designed for gluing: they assume the existence of a set of powerful components and are intended primarily for connecting components together.”
John K.
Ousterhout
http://www.tcl.tk/doc/scripting.html
IEEE Computer
magazine, March 1998
topics
Event-driven & object-orientatedSlide7
P2 Definitions (10)
Should describe the feature – use an example where possible
‘more needed’ this is often whySlide8
Security
Major issue is placing code to run on client’s machine
Cross-site scripting attacks XSS
Vulnerability present in about 70%
pf
web applications (sources,
Veracode
,
Acunetix
)
http://www.veracode.com/security/xss
http
://www.acunetix.com/websitesecurity/cross-site-scripting/Slide9
Security
http
://www.acunetix.com/websitesecurity/cross-site-scripting/Slide10
XSS
Reflective XSS
Malicious
Javascript
in e-mail, victim clicks link,
Javascript
sent to vulnerable website, reflected back and run on victim machine
.
http://www.veracode.com/security/xssSlide11
Persistent attack
Attacker includes malicious script as part of user-name, other users view profile, code executes on other users machine
http://www.veracode.com/security/xssSlide12
Constructs
Need correct construction:
Syntax i.e. Grammar and order correct of words
Dot operator allows an object to use a method
Variable data stored as text or numbers
Must have unique name within script
Loops or iterations code which is executed repeatedly.Slide13
Objects
A type of data which:
Knows things about itself (
properties
)
Knows how to do things (
methods
)
Many objects already exist
Can create new onesSlide14
An example of ‘object’ code...
The ‘String’ object:
<script>
Hw=“Hello World”
document.write
(
Hw.length
)
</script>Slide15
Methods
Each object knows which methods it can carry out,
eg
(string object):
<script>
Hw=“Hello world”
document.write
(
Hw.toUpperCase
())
</Script>
Copy this code and observe the screen output.Slide16
Loops
for
- loops through a block of code a specified number of times
while
- loops through a block of code while a specified condition is true
do...while
- also loops through a block of code while a specified condition is true
for...in
- loops through the properties of an
objectSlide17
Event handling
An event that triggers a piece of code
Some examples and
further explanation are here:
http
://www.w3.org/TR/html4/interact/scripts.html#h-18.2.3Slide18
M2
Client
vs
server is not needed
Compare examples of object-orientated and event-driven
Explain how
Javascript
improves functionality:
Drop-down
menus
Mouse-followers
Image
galleries
Validation
Browser detection
Create cookies
Read/write/modify HTML elements
hiding or showing elements
moving elements
changing
colors
or fontsSlide19
D1
Understanding client-side scripting
Sheryl Canter, April 2004
http://
www.pcmag.com/article2/0,2817,1554984,00.asp