Have you thought about queueing these requests up instead of running them simultaneously? For example, getElementByClass could establish an array of elements and call goAndGetIt on the first element in the array... then the AJAX callback established by goAndGetIt could remove the processed element from the array on completion and call goAndGetIt on the next element, etc., etc.
- Demian
> -----Original Message-----
> From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of
> Michael Beccaria
> Sent: Friday, November 06, 2009 3:01 PM
> To: [log in to unmask]
> Subject: Re: [CODE4LIB] Jquery jsonp question
>
> So I tried some different solutions that were posted and I still can't
> get it to work. Here is my latest attempt as per the advice of Graeme.
> This still pounds my server and freezes my browser. I'm probably going
> to try a different route (static link to an informational page), but I
> wanted to thank everyone who wrote back for their help. Of course, I am
> still open to suggestions if more arise. Here's my latest unsuccessful
> try:
>
> <!cript type="text/javascript">
> var allHTMLTags = new Array();
> function goAndGetIt(thisElement)
> {
> var originalTag = thisElement.innerHTML;
> var issn = originalTag.replace("(","").replace(")","");
>
> $.getJSON("http://library.paulsmiths.edu/issnsearch/ispeerreviewed.php?
> i
> ssn=" + issn + "&jsoncallback=?",function(json, textStatus) {
> thisElement.innerHTML= "(" + issn + ") Peer Reviewed: "
> + json.peerreviewed;
> });
> }
> function getElementByClass(theClass) {
> var allHTMLTags=document.getElementsByTagName("*");
> for (i=0; i<allHTMLTags.length; i++) {
> if (allHTMLTags[i].className==theClass) {
>
> var thisElement = allHTMLTags[i];
> goAndGetIt(thisElement);
> }
>
> }
> }
> window.addEvent('domReady', getElementByClass('SS_JournalISSN'));
> </script>
>
> Mike Beccaria
> Systems Librarian
> Head of Digital Initiatives
> Paul Smith's College
> 518.327.6376
>
>
> -----Original Message-----
> From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of
> Graeme Williams
> Sent: Friday, November 06, 2009 12:49 PM
> To: [log in to unmask]
> Subject: Re: [CODE4LIB] Jquery jsonp question
>
> The following is speculation only lightly leavened by experience.
>
> Here's a simplified example:
>
> for (i=0; i<10; i++)
> {
> var thisArg = ... foo[i].innerHTML ... ;
> // alert("test") ;
> $.getJSON ( "http://somelibrary.org/q=" + thisArg +
> "&jsoncallback=?",
> function(data) {
> foo[i].innerHTML = data.bah
> }
> )
> }
>
> Now, the call to function(){} above creates a function closure, which
> is
> a
> function object linked to its scope. Because Javascript doesn't have
> block
> scope (doesn't create a new scope for each block), the scope of all the
> variables/code in the example above is the same.
>
> What you'd like to happen in the example above is for the $.getJSON
> function
> to be called and the request sent for i=0, then a result returned from
> the
> remote site and the callback called, then the loop start again with
> i=1,
> and
> so on.
>
> What really happens is that Javascript is faster than the network, so
> the
> browser runs through the loop, sending out 10 (asynchronous) requests,
> and
> at the same time the results start to come back. The problem is that
> the
> callback functions for all 10 requests are bound to function closures
> that
> share the same scope, and in particular share the variable "i". This
> means
> that the callback function calls collide with the loop that's sending
> out
> requests.
>
> When you included the call to alert(), you slowed things down so that
> the
> first result did come back before the second request went out, the
> second
> result before the third request, and so on.
>
> I recommend that you try something like this:
>
> function goAndGetIt(thisElement)
> {
> var thisArg = ... thisElement.innerHTML ... ;
> $.getJSON ( "http://somelibrary.org/q=" + thisArg +
> "&jsoncallback=?",
>
> function(data) {
> thisElement.innerHTML = data.bah
> ;
> }
> )
> }
>
> for (i=0; i<10; i++)
> {
> var thisElement = foo[i] ;
> goAndGetIt(thisElement) ;
> }
>
> Each time you call goAndGetIt a new scope is created (with its own copy
> of
> thisElement), so each function closure has its own scope.
>
> Let me know if you'd like a more fully-worked out sample solution for
> your
> problem.
>
> Graeme Williams
> Friend, patron & booster
> Waltham Public Library
> Waltham, MA
