嵌套另一个Ajax请求时，Ajax响应处理被中断

Question

I'm using Ajax requests via Jquery to update some parts of a web page.

Depending on the data values retrieved from the first Ajax request I send (or not) another nested Ajax request to get some more information. Meaning the second Ajax request is nested in the first Ajax response handler.

Basically:

// Get some information
$.ajax({type: "POST", url: get_some_info_url})
  .done(
    function(msg)
    {
      // Given the info contained in msg, let send another request to get more
      if(msg.some_info === true)
      { 
        $.ajax({type: "POST", url: get_some_more_info_url})
           .done(
                function(msg2)
                {
                    // Do something
                }); 
      }

      // Display "Hello world!" whatever the msg.some_info value is.
      $('div#message-id').html("Hello world!");

    });

Different scenarios:

1. If msg.some_info is TRUE => no displaying of "Hello world!"

2. If msg.some_info is FALSE => displaying of "Hello world!"

3. More strange: If I set a breakpoint in the Firefox debugger on the line containing the second nested Ajax call (just stepping over the $.ajax call in the debugger) and msg.some_info is TRUE => displaying of "Hello world!"

I'm a little confused here. Why does my second Ajax call prevent the rest of the code of the first Ajax response from being executed? Is there some "race condition" or session management stuff?

And why breaking in the code "resolves" the issue?

EDIT : ISSUE RESOLVED. See my answer.

Thanks for your help.

Answer 1

I'm not sure you should test for truth with === operator.

According to your comments,

// Given the info contained in msg, let send another request to get more

you just want to check if

msg.some_info

exists at all. In this case it's better to check by writing

if(msg.some_info) {
    /* Your code here*/
}

Another variant why msg.some_info is true but the "Hello world" isn't displayed is that your code hasn't response from the server and waits for it. Because you wrote "just stepping over the $.ajax call in the debugger) and msg.some_info is TRUE => displaying of "Hello world!"". So you step over that "bad point" and the message is diplayed than. That makes me think that there're some problems either in the code itself or in the server response which is not got back.

Answer 2

The issue was on my side, sorry for wasting your time.

Actually I was erasing the "hello world!" text in the second Ajax response processing. Hence the difference between debugging run and normal run. The sequence for handling ajax responses was not the same with and without debugging hence misleading me about the root cause of the issue.

Thank you all for your help.