ITEC 325 2012spring ibarland

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lect01a
intro: web requests and responses

• When you visit a web page, what happens?
  • A file: http://www.radford.edu/ibarland/Info/proofreader-marks.html
  • A directory: http://www.radford.edu/ibarland/Info/
  • Another directory: http://www.radford.edu/ibarland/
  • No file specified: http://www.radford.edu/
  • File doesn't exist:http://www.homestarrunner.com/asdfasdfasdf
    (Btw, here's a 5-min TED talk on how a business can learn from rethinking its 404 page experience. The first 3min are annoying, but the final lesson is sound.)
  • A page with GET params (navigate from nytimes.com: e.g. page-2)
  • Something hairy like http://maps.google.com/?ll=37.235094,-80.420677&spn=0.000536,0.000916&hnear=1600+N+Main+St,+Blacksburg,+Virginia+24060&t=h&z=20&vpsrc=6
  • What about http://sn.im/bburg-roundabout?
  • A basic php page: hello-world1.php
  • hello-world1.html (same content but saved with suffix “html”)

  For this class, I recommend Chrome, or Firefox w/ Firebug. We will not try to support IE!

          Client                             Server
  
          Browser            ->request->
                              (URL)
                                             WebServer (Apache)
                                               - look up file:
                                               - possibly redirect...
                                               - what if file exists, but no permissions?
                                               - what if file doesn't exist?
                                               - what if URL is a directory?
                                               - what if request from a mobile platform?
                                               - process any php (as configured)
                                                 which may invoke other programs, db connections, etc
                              <-response<-
                              (html, jpg,
                               html+javascript,
                               ...)
          
         Browser
          ...makes a gui window,
             lays out text/color/pictures
             Displays response
          Also:
          ...makes add'l URL requests... [Ad blocker!]
          ...runs javascript...
          ...invokes plug-ins or passes to OS...
  
          
          Q: are URLs case-sensitive?
          
          
          HTTP response codes
  
  
  
  
  
  
         
  
  
   
          
          
  
  
          
  

• Running php from the command line.
  To run interactively: php -a
• Show-source of:
  1. hello-world1.php (a basic php page)
  2. hello-world1.html (same content but saved with suffix “html”)
  3. hello-world0.html (a plain page with no php at all)
  4. hello-world0.php (same plain page but saved with suffix “php”)
  (Permissions.)
• Go over course-info sheet.
(Reached here, lect01a.)
• Show source, and discuss evolution of the javascript program. For each one: how much work is it to add another category (animal)?
  1. hiding-parts-v0.html (A first version, copied from one person to another. C-)
  2. hiding-parts-v1.html (A small tweak, greatly reduces length of code. B)
  3. hiding-parts-v2.html (Generalize -- much nicer. A)
  4. hiding-parts-v3a.html (Generalized (but, arguments more abstract). A+)
  5. hiding-parts-v3b.html (As before, but placing the paragraph in a different place suddenly breaks the code?! It's because the processing happens ASAP, before the named id has been parsed by the browser. An error message like 'no such id' would have been very nice!¹ Had my first attempt suffered from this bug, I would have given up assuming my whole approach didn't work.
     See also: attribute defer for tag script.
  6. hiding-parts-v3c.html, Pulling the javascript into its own file (can now be re-used between many pages). (It also demo's how you really can easily call the function twice in the same page w/o repeating code, which we could have done ever since we made createNavBar its own function.)
• Applying the above: How can/should we generalize a Bingo card javscript?

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©2012, Ian Barland, Radford University Last modified 2012.May.31 (Thu)

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