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Message-ID: <1847393.YeQSDktdzs@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Thu, 06 Sep 2012 21:49:32 +0200
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Subject: Re: XHR: Passing Parameters to a ready-state-change Function
Newsgroups: comp.lang.javascript
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Xref: csiph.com comp.lang.javascript:15750

Thomas 'PointedEars' Lahn wrote:

> Stefan Weiss wrote:
>> […]
>>   function fetch (url, callback) {
>>       // (minimal example)
>>       var xhr = new XMLHttpRequest();
>>       xhr.open("GET", url, true);
>>       xhr.onreadystatechange = function () {
>>           if (xhr.readyState == "4") {
>>               callback(xhr.responseText);
>>           }
>>       };
>>       xhr.send();
>>   }
>> […]
>> 
>> What am I missing?
> 
> At first glance, that the `readyState' property values are of type Number,
> and that xhr.send(null) should be called with GET.

At second glance, that readyState == 4 does not need to mean success (you 
have to check the `status' as well) and that `callback' has no idea whether 
an empty `responseText' means success or failure.  I think that should be 
fixed even in a minimal XHR example:

  function fetch (url, callback)
  {
    /* (minimal example) */
    var xhr = new XMLHttpRequest();
    xhr.open("GET", url, true);
    xhr.onreadystatechange = function () {
      if (xhr.readyState == 4 && xhr.status == 200)
      {
        callback(xhr.responseText);
      }
    };
    xhr.send(null);
  }

BTW, it is acceptable to see that you also use the space-before-parameter-
list convention.  It makes calls so much easier to find, does it not?


PointedEars
-- 
var bugRiddenCrashPronePieceOfJunk = (
    navigator.userAgent.indexOf('MSIE 5') != -1
    && navigator.userAgent.indexOf('Mac') != -1
)  // Plone, register_function.js:16