What is the cleanest way to get the progress of JQuery ajax request?

In plain javascript is very simple: need just to attach the callback to {XMLHTTPRequest}.onprogress

var xhr = new XMLHttpRequest();

xhr.onprogress = function(e){
    if (e.lengthComputable)
        var percent = (e.loaded / e.total) * 100;
};

xhr.open('GET', 'http://www...', true);
xhr.onreadystatechange = function() {
    ...
};
xhr.send(null);

but I'm doing an ajax site that download html data with JQuery ($.get() or $.ajax()) and I was wondering which is the best way to get the progress of a request in order to display it with a little progress bar but curiously, I'm not finding anything usefull in JQuery documentation...

Something like this for $.ajax (HTML5 only though):

$.ajax({
    xhr: function() {
        var xhr = new window.XMLHttpRequest();
        xhr.upload.addEventListener("progress", function(evt) {
            if (evt.lengthComputable) {
                var percentComplete = evt.loaded / evt.total;
                //Do something with upload progress here
            }
       }, false);

       xhr.addEventListener("progress", function(evt) {
           if (evt.lengthComputable) {
               var percentComplete = evt.loaded / evt.total;
               //Do something with download progress
           }
       }, false);

       return xhr;
    },
    type: 'POST',
    url: "/",
    data: {},
    success: function(data){
        //Do something on success
    }
});

jQuery has already implemented promises, so it's better to use this technology and not move events logic to options parameter. I made a jQuery plugin that adds progress promise and now it's easy to use just as other promises:

$.ajax(url)
  .progress(function(){
    /* do some actions */
  })
  .progressUpload(function(){
    /* do something on uploading */
  });

Check it out at github

I tried about three different ways of intercepting the construction of the Ajax object:

1. My first attempt used xhrFields, but that only allows for one listener, only attaches to download (not upload) progress, and requires what seems like unnecessary copy-and-paste.
2. My second attempt attached a progress function to the returned promise, but I had to maintain my own array of handlers. I could not find a good object to attach the handlers because one place I'd access to the XHR and another I'd have access to the jQuery XHR, but I never had access to the deferred object (only its promise).
3. My third attempt gave me direct access to the XHR for attaching handlers, but again required to much copy-and-paste code.
4. I wrapped up my third attempt and replaced jQuery's ajax with my own. The only potential shortcoming is you can no longer use your own xhr() setting. You can allow for that by checking to see whether options.xhr is a function.

I actually call my promise.progress function xhrProgress so I can easily find it later. You might want to name it something else to separate your upload and download listeners. I hope this helps someone even if the original poster already got what he needed.

(function extend_jQuery_ajax_with_progress( window, jQuery, undefined )
{
var $originalAjax = jQuery.ajax;
jQuery.ajax = function( url, options )
{
	if( typeof( url ) === 'object' )
	{options = url;url = undefined;}
	options = options || {};

	// Instantiate our own.
	var xmlHttpReq = $.ajaxSettings.xhr();
	// Make it use our own.
	options.xhr = function()
	{return( xmlHttpReq );};

	var $newDeferred = $.Deferred();
	var $oldPromise = $originalAjax( url, options )
	.done( function done_wrapper( response, text_status, jqXHR )
	{return( $newDeferred.resolveWith( this, arguments ));})
	.fail( function fail_wrapper( jqXHR, text_status, error )
	{return( $newDeferred.rejectWith( this, arguments ));})
	.progress( function progress_wrapper()
	{
		window.console.warn( "Whoa, jQuery started actually using deferred progress to report Ajax progress!" );
		return( $newDeferred.notifyWith( this, arguments ));
	});

	var $newPromise = $newDeferred.promise();
	// Extend our own.
	$newPromise.progress = function( handler )
	{
		xmlHttpReq.addEventListener( 'progress', function download_progress( evt )
		{
			//window.console.debug( "download_progress", evt );
			handler.apply( this, [evt]);
		}, false );
		xmlHttpReq.upload.addEventListener( 'progress', function upload_progress( evt )
		{
			//window.console.debug( "upload_progress", evt );
			handler.apply( this, [evt]);
		}, false );
		return( this );
	};
	return( $newPromise );
};
})( window, jQuery );

jQuery has an AjaxSetup() function that allows you to register global ajax handlers such as beforeSend and complete for all ajax calls as well as allow you to access the xhr object to do the progress that you are looking for

http://www.htmlgoodies.com/beyond/php/show-progress-report-for-long-running-php-scripts.html

I was searching for a similar solution and found this one use full.

var es;

function startTask() {
    es = new EventSource('yourphpfile.php');
  
//a message is received
es.addEventListener('message', function(e) {
    var result = JSON.parse( e.data );
      
    console.log(result.message);       
      
    if(e.lastEventId == 'CLOSE') {
        console.log('closed');
        es.close();
        var pBar = document.getElementById('progressor');
        pBar.value = pBar.max; //max out the progress bar
    }
    else {
        
        console.log(response); //your progress bar action
    }
});
  
es.addEventListener('error', function(e) {
    console.log('error');
    es.close();
});

}

and your server outputs

header('Content-Type: text/event-stream');
// recommended to prevent caching of event data.
header('Cache-Control: no-cache'); 

function send_message($id, $message, $progress) {
    $d = array('message' => $message , 'progress' => $progress); //prepare json
  
    echo "id: $id" . PHP_EOL;
    echo "data: " . json_encode($d) . PHP_EOL;
    echo PHP_EOL;
  
   ob_flush();
   flush();
}


//LONG RUNNING TASK
 for($i = 1; $i <= 10; $i++) {
    send_message($i, 'on iteration ' . $i . ' of 10' , $i*10); 

    sleep(1);
 }

send_message('CLOSE', 'Process complete');

Follow the steps to display Progress of Ajax Request:

1. Create a Spinner using Html & CSS or use Bootstrap Spinner.
2. Display the Spinner when the end-user is requesting for the AJAX Data for infinite loop or for threshold limit time.
3. So, after a SUCCESS / ERROR result of AJAX Request, remove the Spinner which is currently displayed and show your results.

To make it easy I recommend you using JS Classes for dynamically Displaying & Hiding the spinner for this purpose.

I Hope this helps!