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Re: XHR: Passing Parameters to a ready-state-change Function

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Tim Streater wrote:

> Gene Wirchenko <genew@ocis.net> wrote:
>> > By the way, as has been pointed out you need to check that status==200
>> > also. You also need to set xhr = null when you've finished with it.
>> 
>>      I know about 200.

Do you know about 0 and 1223 (sic!) as well?

>>      Setting xhr to null?  Why?  I may well be using it again.  The
>> forms are CRUD and so there may be multiple transactions go to the
>> server.

ACK.

> And each time you call your ajax function you'll get a new one.

Which is not a bad thing.

> AIUI, although my knowledge of closures is a bit limited, each one will
> live forever unless you explicitly dump it when you've finished with it.
> By setting it to null, it'll get garbage-collected subsequently.

Wishful thinking.  There is no guarantee that garbage collection will 
commence before all browser windows are closed.
 
> Here's what I do (slightly simplified, as I log the status error rather
> than just alert-ing):
> 
> function ajax (url, data, callbackFunction)
>      {
> 
>      var request = window.XMLHttpRequest ? new XMLHttpRequest () : new
> ActiveXObject ("MSXML2.XMLHTTP.3.0");
> 
>      request.open ("post", url, true);
>      request.setRequestHeader ("Content-Type",
> "application/x-www-form-urlencoded; charset=utf-8");
>  
>      request.onreadystatechange = function ()
>           {
> 
>           if  (request.readyState!=4)  return;
> 
>           if  (request.status==200 && request.responseText!="")
> callbackFunction (request.responseText);
>           if  (request.status!=200)  alert ("Bad ajax status: " +
> request.status);
> 
>           request = null;

With regard to memory efficiency and probably even runtime efficiency, it
is far better to reuse an existing XHR object once the request has been 
processed.  See JSX:http.js [1] for example.
 
>           };
> 
>      request.send (data);

`data' needs to be transfer-encoded; with this Content-Type header field 
value and without a Transfer-Encoding header field, it needs to be percent-
encoded:

  request.send(encodeURI(data));

But you might want to encodeURIComponent() each name an value separately 
instead.


PointedEars
___________
[1] 
<http://pointedears.de/websvn/filedetails.php?repname=JSX&path=%2Ftrunk%2Fhttp.js>
-- 
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
  -- Richard Cornford, cljs, <f806at$ail$1$8300dec7@news.demon.co.uk>

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XHR: Passing Parameters to a ready-state-change Function Gene Wirchenko <genew@ocis.net> - 2012-09-05 13:53 -0700
  Re: XHR: Passing Parameters to a ready-state-change Function Jim T. <x@y.z> - 2012-09-05 17:46 -0400
    Re: XHR: Passing Parameters to a ready-state-change Function Gene Wirchenko <genew@ocis.net> - 2012-09-05 17:30 -0700
      Re: XHR: Passing Parameters to a ready-state-change Function Jim T. <x@y.z> - 2012-09-05 20:55 -0400
  Re: XHR: Passing Parameters to a ready-state-change Function Jim T. <x@y.z> - 2012-09-05 21:43 -0400
    Re: XHR: Passing Parameters to a ready-state-change Function Jim T. <x@y.z> - 2012-09-05 21:49 -0400
  Re: XHR: Passing Parameters to a ready-state-change Function Stefan Weiss <krewecherl@gmail.com> - 2012-09-06 18:56 +0200
    Re: XHR: Passing Parameters to a ready-state-change Function Gene Wirchenko <genew@ocis.net> - 2012-09-06 10:55 -0700
    Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-06 21:38 +0200
      Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-06 21:49 +0200
    Re: XHR: Passing Parameters to a ready-state-change Function Gene Wirchenko <genew@ocis.net> - 2012-09-06 15:49 -0700
      Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-07 09:15 +0100
        Re: XHR: Passing Parameters to a ready-state-change Function Gene Wirchenko <genew@ocis.net> - 2012-09-07 09:58 -0700
          Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-07 19:14 +0100
            Re: XHR: Passing Parameters to a ready-state-change Function cezary.tomczyk@gmail.com - 2012-09-07 13:51 -0700
              Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-08 00:52 +0200
                Re: XHR: Passing Parameters to a ready-state-change Function cezary.tomczyk@gmail.com - 2012-09-07 16:32 -0700
                Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-08 09:48 +0200
                Re: XHR: Passing Parameters to a ready-state-change Function Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-09-08 02:09 -0700
                Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-08 11:09 +0100
                Re: XHR: Passing Parameters to a ready-state-change Function Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-09-08 03:39 -0700
                Re: XHR: Passing Parameters to a ready-state-change Function John G Harris <john@nospam.demon.co.uk> - 2012-09-08 15:00 +0100
            Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-07 23:44 +0200
              Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-07 23:08 +0100
                Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-08 00:46 +0200
                Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-08 11:11 +0100
                Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-08 14:21 +0200
                Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-08 17:06 +0100
                Re: XHR: Passing Parameters to a ready-state-change Function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-09-08 20:41 +0200
                Re: XHR: Passing Parameters to a ready-state-change Function Dr J R Stockton <reply1236@merlyn.demon.co.uk.invalid> - 2012-09-09 20:04 +0100
            Re: XHR: Passing Parameters to a ready-state-change Function Gene Wirchenko <genew@ocis.net> - 2012-09-09 18:40 -0700
              Re: XHR: Passing Parameters to a ready-state-change Function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2012-09-10 07:21 +0000
              Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-10 09:03 +0100
                Re: XHR: Passing Parameters to a ready-state-change Function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2012-09-10 13:59 +0000
                Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-10 15:35 +0100
                Re: XHR: Passing Parameters to a ready-state-change Function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2012-09-10 22:42 +0000
                Re: XHR: Passing Parameters to a ready-state-change Function Scott Sauyet <scott.sauyet@gmail.com> - 2012-09-11 10:09 -0700
                Re: XHR: Passing Parameters to a ready-state-change Function Tim Streater <timstreater@greenbee.net> - 2012-09-11 22:42 +0100

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