Monday, October 4, 2010

How to Stop an Ajax request in prototype.js

Question is what will you do if you are using prototype.js(which is not having any abort method) for making a Ajax request and due to some circumstance you want to abort the ajax request raised. Well one can think that this is a narrow requirement, why will anybody need to do this because in the meantime request will be done and one might be having the response in return from server.

I hit this corner case where page content was loading from an Ajax request and which after rendering was firing another Ajax request to update the paginate-r(which is also self firing the request on response completion), but to my surprise i was not able to control the "Ajax request to update paginate-r" and hence i am creating the self firing request but am not able to destroy them.

And i don;t know for what reason there is no "ajaxRequest.abort()" method. And i found the answer from a narrow corner of http://blog.pothoven.net/2007/12/aborting-ajax-requests-for-prototypejs.html and it worked and just to increase the find-ability of this solution am re-writing the post.

introduce a method abort like this for prototype.js
Ajax.Request.prototype.abort = function(){
this.transport.onreadystatechange = Prototype.emptyFunction(); //prevent state change callbacks from being issues
this.transport.abort(); //abort the XHR
Ajax.activeRequestCount--; //updates the request counter
};

and then in your code
write it somewhere so that it is executed only once
<script>
var cw_paginator_request = null;
</script>

and then to assign the request if null else abort the request and fire a new request, like this
<script>
if(cw_paginator_request != null){
cw_paginator_request.abort();
}
cw_paginator_request = <%=remote_function(:url => {:controller => "some_controller", :action => "update_paginator", :id => @selected_id }) -%>;
</script>

Hopefully it might help somebody in need :)

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