I have a similar question like this,
http://www.experts-exchang
I do encounter similar problem randomly that xhr.status is 0 when xhr.readyState is 4. I've been researching online and found there is no case for http request to return 0.
In that answered question, I don't quite get the meaning of the solution. Could someone shed more light on this? In what case xhr.status would be 0? Is
if (xhr.status == 200 || xhr.status == 0)
a good solution for this after all?
Thanks.
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Opalelement,
Hello again :)
When the readyState becomes 4, why would status remain at the default value 0?
And I don't quite understand what you mean "if the status changes from the 0, it can't go back"... if (xhr.status == 0) stands true, I can't tell if it has changed or not. And what if the http response is not "200 OK" after all?
Thanks.
The status and readystate are different. The status is what is returned by the web page you send a request to. The readystate is the XMLHttpRequest telling you if it is ready to send a request or not. To see the readystates, go here: http://www.w3schools.com/a
The reason the readystate is already at 4 is because once you create the XMLHttpRequest object, it will update the readystate to say it is ready (which is 4).
Yes, I understand what readyState and status properties mean and I know how it works. However, what I see is that (not every time, only like 5%)
when readyState is 4, which means all the data has been received and there is a http response code that is stored in status property. However, sometimes status is 0 instead of some meaningful response, such as 200, 3xx, 4xx, 5xx.
I just don't understand why the status is 0 when all data (plus http response) has been received.
I don't know if this helps at all or will just confuse things even more. I've been doing a lot of work with ajax lately, lost of coding and that generally means lots of typos and errors and bugs that need to be found. I've also come across times when I get back a response of 0, or to be more accurate, a status of FALSE. In most cases I would expect to see a 404 status because what cased the error is the fact that I made a typo and called a script the didn't exist.
So, there's that to add some confusion to the mix.
Getting a online demo is not going to help on this problem, because when the problem occurs, all you can see is a dialog showing some error message when the code finds out the status returns 0.
The code for making the ajax calls is similar to all the samples on the web. And the ajax is making a call to a php which does some database thing. We have traced the code that the php does not return any error and we are expecting a 200 OK but the returned status property is 0 in a random manner.
I thought a lot of people would see similar problem, because I saw this same problem in another project (totally different code and application).
Hi Badotz,
the code is similar to the examples about making AJAX calls on the net. For example, someone asked similar question before,
http://www.experts-exchang
where there is a sample code. And I just use similar code.
Thanks.
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by: OpalelementPosted on 2009-11-02 at 06:32:39ID: 25719609
Hello, as you can see I answered that other question so I will try to help with this :)
The status of the XMLHttpRequest for Webkit and Mozilla is, by default, 0. This 0 is only there before a request is sent. However, once a request is sent, it reurns as 200 to say it was successful. After this it can never go back to 0 without reloading the page.
The order can be like this:
1) Page loads, status is 0.
2) A request is sent using the object.
3) Status returns as 200.
IE sets the default to 200 instead of 0, but all the 0 is there for is basically a null to say nothing has happened yet.
Therefor, using the following code will not be any risk, as once the status changes from the 0 it can't go back.
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