AJAX event for when the server receives the request - before processing it

Question

I'm currently developing a class in PHP that makes cURL requests and returns the answer as JSON for it to be processed by jQuery on my page. So far — no problems. (Note that the only way for me to load that content is by using my own server - I'm querying a website's API with my private API key)

The problem is that some pages are slow (because of their server), and that plus the request to my server with jQuery makes it long to load a page, which makes around 5 seconds (or more) with no feedback at all for the user.

What I was wondering if there's any jQuery event for $.ajax which is called when the request is sent to the server (meaning that the server also started loading the requested page), but before the actual request to my page ended.

I'm trying to achieve this:

*user click* (0)
Sending request... (1)
Request sent. Loading page... (2)
Page loaded. (2)

• Event 0 would be just a click
• Event 1 would be jQuery's $.ajax({ beforeSend: function(){} );
• Event 2 is what I want. It'd be something like onSend, but sadly it doesn't exist
• Event 3 would be jQuery's $.ajax({ complete: function(){ } });

As a side note: I'm using jQuery, but I have no problems in using plain JavaScript if needed.

Answer 1

The Ajax have the default events that can be handled with here on the reference: http://api.jquery.com/jquery.ajax/

But i'll do a sample to you see how it works.

The HTML code for a sample:

<input type=button id=yourButtonID name=yourButtonID>

-> (0) - The onClick event.

$("#yourButtonID").click(AjaxFunction());

-> (1), (2), (3) The AjaxFunction.

function AjaxFunction(){

  $.ajax({
    url: "http://www.stackoverflow.com"
  }).beforeSend(function() {
    //show the ajax image
  }).done(function(data) {
    alert(data);
  }).fail(function() {
    alert("sorry, it failed");
  }).success(function() {
    alert("Sucess!");
  });
}

If you want to show to the user that the Request is happening, you just need to show to the user a ajax loading image on the beforeSend event, like that one:

Something like onSend is the beforeSend because it executes before sending, and while are you sending, why you would fire a event?

Basically, ajax is a useful tool to make XHR's (XMLHTTPRequest's) that have pre-made events that you can use before you send the request, when your request is done, and if it fails, and if it success.

Answer 2

Basically, you want two responses from server: the first as soon as it receives your request, and the second containing the payload from the other server.

Since a regular ajax HTTP request can only have one response, you could use web sockets instead. This allows the server to 'push' data to the client.

see the links below:

https://developer.mozilla.org/en-US/docs/WebSockets

http://www.html5rocks.com/en/tutorials/eventsource/basics/