XMLHttpRequest onreadystatechange called multiple times

Question

I am implementing a login system in php and using ajax requests.

this is my request

hr.open("POST", url, true); hr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");  hr.onreadystatechange = function() {      var return_data = hr.responseText;     if(hr.readyState == 4 && hr.status == 200) {         alert('is logged');     }else if (hr.status == 400){         alert('is not logged');     } }   hr.send(vars); // Actually execute the request 

but when i get the response back the browser launches various alerts. Can anyone help how to fix this?

Answer 1

Yeah its working as it should.......onreadystatechange may be called several times in one request.. And for alerting both the conditions is that whenever the request is okay that is 200.

It alerts :

'its not logged'

and when it got readystate=4 as well as Ok signal it alerts:

logged in.

Then

readyState =4 --> request finished and response is ready

status= 200 --> it means the request is successfully handled by the Server.

So, 2nd alert popup because at least your request was successfully handled. For more info: https://www.w3schools.com/js/js_ajax_http_response.asp

Here it is:

      xhrobj.onreadystatechange = function()     {       if (xhrobj.readyState == 4 && xhrobj.status == 200)       {         if (xhrobj.responseText)          {                 //put your code here             document.write(xhrobj.responseText);           }        }      };