What I'm asking is conceptual rather than why my code doesn't work. I'm trying to make a web app that displays content fetched from a database in a sequence, one at a time, and then waits for a response from the user before continuing to the next one. I'm working with javascript on the client side with the JQuery library and php on the server side.

In theory, there's time while waiting for the user's input to fetch information from the server using an AJAX request and have it ready for the use by the time he clicks the button, but there's also a chance that such an AJAX request hasn't completed when he clicks the button. So I need something like

pseudocode:

display current information

fetch next data point from the server in the background

onUserInput { 
    if ( ajax request complete) {

    present the information fetched in this request

    } else if (ajax request not complete)  {

    wait for ajax request complete  

    present information to user }

My question is this: how does one implement this " else if (ajax request not complete) { wait for ajax request complete " part.

I'm currently using JQuery for my AJAX needs. I'm somewhat new to working with AJAX, and I did search around, but I didn't find anything that seemed on point. I don't know what tools I should use for this. Some kind of queue maybe? I don't need to be spoon fed. I just need to know how this is done, using what tools or if my desired outcome would be accomplished in some other way entirely. Thanks.