gistfile1.js

// Asynchronous coding takes a bit of time to wrap your head around.

// I can't know for sure, but I think you misunderstand the general 
// nature of a callback function. 'ajax.post' doesn't wait for the 
// request to complete before returning, if it did so, there wouldn't
// be any need for a callback. **If you want something to happen AFTER
// the request completes, you have to put it in the callback function.**
// Don't think of a callback as some kind of icing on the cake, it is
// literally the continuation of your program's logic.

// To see this better, it helps to use *anonymous functions*, that is, 
// instead of assigning a function to a variable and then referencing
// it as a callback, put the function directly into 'ajax.post'.

function meal() {
  ajax.post("http://example.com/get_soup", function(soup) {
    eat(soup);
    ajax.post("http://example.com/get_steak", function(steak) {
      eat(steak);
      ajax.post("http://example.com/get_cake", function(cake) {
        eat(cake);
      });
    });
  });
}

// Or, if you like setting variables:

function meal() {
  var soup;
  var steak;
  var cake;
  ajax.post("http://example.com/get_soup", function(s) {
    soup = s;
    ajax.post("http://example.com/get_steak", function(s) {
      steak = s;
      ajax.post("http://example.com/get_cake", function(c) {
        cake = c;
        
        eat(soup);
        eat(steak);
        eat(cake);
      });
    });
  });
}