CODEWITHSUNDEEP
javascriptajax
Rama Rao M
Rama Rao M

Reputation: 3051

Does Ajax block the window while processing the request?

I am making an ajax request where it may take much time to process the server-end.So I want to show a loading image at the time of request process.But loading image is not being shown while ajax requst.

var ref = createAjaxRequest();//Ajax req is created here...
if(ref){
        showLoadingImg();
        ref.open('POST','x.jsp',false);
        ref.onreadystatechange = eventStateChange;
        ref.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        ref.setRequestHeader("Connection", "keep-alive");
        ref.send();
    }
    else{ alert("Your browser does not support this feature");
}
function eventStateChange(){
 if(ref.readyState==4 ){
    //processing response here......
   hideLoadingImg();
 }
}

function showLoadingImg();{
 /* <div id="ajaxLoading">(with background image is in page)
  It is displayed properly when I set display:inline 
  manually through developer tools of a browser.</div>
*/
  document.getElementById('ajaxLoading').style.display='inline';
}
function hideLoadingImg();{
  document.getElementById('ajaxLoading').style.display='none';
}

is there anything wrong?

I tried to debug and found that:

  1. Though showLoadingImg() is called before open() method, the loading image is displayed on browser only after ref.readyState==2.

  2. But unfortunately time gap between readyState==2 and readyState==4 is very less, the loading image is immediately hidden.
    Thus user cannot see the loading image...

So, what I am doubting is, doesn't ajax run the script unless it goes to readyState==2.

Upvotes: 0

Views: 248

Answers (2)

user1882085
user1882085

Reputation: 26

I thinks your call to open is wrong. The third argument (boolean) indicates if the request is asynchronous or not.

Consider complete documentation here : http://www.w3schools.com/ajax/ajax_xmlhttprequest_send.asp

ref.open('POST','x.jsp',true);

Should solve your problem.

Regards

Upvotes: 1

Quentin
Quentin

Reputation: 943207

XMLHttpRequest blocks if you set async to false as you do with the third argument here: ref.open('POST','x.jsp',false);.

Upvotes: 2

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