1. JavaScript (ii)
Prof. Alvarado
MDST 3703/7703
4 October 2012

2. Business
• Midterms to be on Collab early this evening
– They will be due next Thursday at Midnight
• No readings over Fall Pause
– But you may want to brush up on your HTML, CSS,
and JavaScript
– See the Resources Page on the course blog

3. Business
• Can you access your Home Directory on the web?
– Test by going to the URL in your browser, not the file on
your computer.
• Does your page point to the right resources?
– The JavaScript and CSS elements must point to the right
path
– You can copy these resources into your directory if you
want
• Does your jQuery code reference the right names?
– Remember, the selectors must point to names that exist in
the DOM

4. Review
• JavaScript is a programming language that is
built into the web browser
– Source code
– Algorithmic
– Input/output of data
• Variants exist
– ActionScript (Flash)
– Jscript (Internet Explorer)
– ECMAScript (standard)
• jQuery is a library of JavaScript functions that
makes hard things easier

5. Comments

6. Does JavaScript allow us to overcome mistakes in the
initial coding by setting the behavior to take care of
such problems? For example, if we have hundreds of
pages of marked-up content, it is quite possible that a
mistake will lead to a missing chapter number
somewhere. We can use JavaScript to make sure that
in such cases it should display “missing chapter
number” so that readers (including authors) are aware
of it. Therefore, is JavaScript ever used as a fail-safe, or
are problems usually taken care of in previous layers of
web design?
Yes, in a sense. You can can JS for “web scraping”
and other kind of post-processing where you don’t
control the source. But usually you want to fix the
source if you can.

7. Is there an easy way of proofreading markup language
for errors, or does the creator have to read through
every character in the file any time there is a problem?
Yes – it’s called ‘debugging,’ and
there are tools to help with that.
There are debugging tools built
into your browser.

8. The reason I am almost laughing about it now is that it’s
ridiculous to me that even when one seems to follow all
the “rules” of coding or using a computer, sometimes
inexplicable things come up that completely disrupt or
negate all your work. As much as we know about and
understand computers, we don’t always have rhyme or
reason for why computers do what they do.
Three engineers were aboard a stopped train …

9. Will there ever be an easier way to create digital
documents?
Yes: blogs and wikis, for example,
make page creation easy.
But if you want to process lots of
source data, or create HTML pages on-
the-fly, you need to know the code.

10. I find that as we delve into more complex programming
languages, I am having a harder time grasping the
necessary steps. Should this be the case?
YES.

11. Would it not be easier to control the structure, style, and
behavior of a web page with one markup language, in
one file?
What was the motivation for having all of these web
languages interact with each other?
It would be nice, but this is kind of like wishing
humans had one language. The web is a vast,
evolving system, and these languages were created
at different times to solve different problems.
One reason they are separated is because different
people do the coding for each layer.

12. I don’t understand how we can insert a new language
into HTML using a new tag in the header, without it
being a part of the HTML?
HTML is a source code that can hold lots of
different content, including programming code.
But the code and the content are treated
differently by the browser in producing the
resulting page that you see.

13. Exercises
• Overview of JavaScipt
– Follow along
– Either copy my source code or write it as I
demonstrates
• A simple footnote system