./ajax/synchronous-ajax.txt

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12:30 -!- multi_io [n=olaf@rosa.physik-pool.TU-Berlin.DE]
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19:29 < multi_io> am I right in assuming that there's no way to implement a JS function that fetches and
                  returns a web page using Ajax? (because XMLHttpRequest can only be used asynchronously, and
                  the JS engine is single-threaded)
19:29 < phpboy> multi_io: it is possible
19:30 < phpboy> VERY possible... lemme paste you a link to help.. hang 10...
19:30 < multi_io> well, it can be used synchronously, but on some browsers the synchronous call appears to
                  return before the request is complete
19:30 < phpboy> multi_io: http://prototype.conio.net/ <--- that should get you started, if I understand what
                you wanna do correctly
19:34 < multi_io> phpboy: after skimming http://www.prototypejs.org/learn/introduction-to-ajax , I'd say that
                  that library only has an an asynchronous programming model, so it wouldn't get around the
                  problem


19:44 < multi_io> there's no sleep() function in JS that allows events to be processed while it blocks, is
                  there?


19:46 < chupacabra2> multi_io: setTimeout. Create an anonymous function that would finish your processing job,
                     and setTimeout it for whatever amount of time you want
19:47 < multi_io> chupacabra2: I know setTimeout, but that's not what I want, because it's asynchronous
19:48 < chupacabra2> multi_io: but how can you have synchronous and "allow events to be processed"?
19:48 < chupacabra2> multi_io: "allow events to be processed" is asynchronous by definition :)
19:48 < multi_io> not necessarily
19:48 < multi_io> it could switch stacks internally
19:49 < chupacabra2> multi_io: Please elaborate on what result you want to get :)
19:49 < multi_io> think of functions like messageBox() or getMessage() in GUI APIs, if you've ever used those
19:50 < chupacabra2> Ah - they fire away, your main execution flow is blocked, but other stuff may happen.
                     Whenever "something" occurs, your main execution flow takes place again. Like that?
19:50 < multi_io> messageBox("Hello!") displays the box and blocks until the user has clicked OK, but still,
                  events are processed while the box is displayed
19:51 < multi_io> there are different strategies to implement that, even when using only a single thread
19:51 < chupacabra2> Yea, doing that right now. Lots of callbacks ;)
19:52 < multi_io> one would be that messageBox() again polls the event queue internally and runs your event
                  handlers (so they're executed on the same call stack as the messageBox() call)
19:52 < chupacabra2> But how does one apply that to sleep()? (which does not need to return a result, and
                     which should sleep for some fixed time and does not react to anything happening)
19:53 < multi_io> stop polling the event queue when the sleep time has run out
19:54 < chupacabra2> So setTimeout is not acceptable, since things
                     might come out of setTimeout in wrong order?
19:54 < multi_io> setTimeout is acceptable, but it'S more inconvenient to use
19:54 < multi_io> asynchronous programming is inconvenient
19:54 < fatbrain> javascript is synchronous by nature
19:55 < multi_io> it's essentially impossible to implement something like
                  pageContent=fetchPage("http://myhost.com/x/y")
19:56 < chupacabra2> multi_io: you can, if they ship their data as JS file
19:56 < chupacabra2> otherwise, xss will stop you
19:56 < multi_io> you'd always have a programming model like asyncFetchPage("http://myhost.com/x/y",
                  function(pageContent){.....})
19:57 < chupacabra2> multi_io: yea
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