Question

I have a little question. say i have a js function

$(function() {
 $(".button").click(function(){ 
 var id=$(this).attr('id');
 var dataString = 'id='+ id ;
 $.ajax({
   type: "POST",
   url: "download_number.php",
   data: dataString,
   cache: false,
   success: function(html)
   {
     $("#div_"+id).html(html);
   }  });
   window.open('File_download.php?file_id='+id, '_blank' );
  });

as you can see window.open call is after $.ajax call

Does it guaratee that $.ajax call will get executed every time before the page reloads and if no then

shouldn’t we declare window.open in success function?

In my opinion when there is slow response from server the page will reload first and it may happen that $.ajax call will be interrupted by window.open function

but i get a downvote for the same reason here stackoverflow.com/questions/12908138/how-to-get-the-id-or-name-of-related-file/

And Thanks for making my belief stronger

Answer 1

In your example, the window.open function will always (!) be called before the success callback function given to the ajax call. Ajax traffic is always asynchronous, whereas the window.open function resides in the synchronous JS <script> tag.

Since JavaScript is single-threaded, all synchronous statements will always be executed before any asynchronous functionality like ajax setTimeout animate etc.

$.ajax({
   type: "POST",
   url: "download_number.php",
   data: dataString,
   cache: false,
   success: function(html) { // asynchronous functionality
     $("#div_"+id).html(html);
   }  
}); 
// within synchronous script statements
window.open('File_download.php', '_blank' );