JavaScript Global variables after Ajax requests

Question

the question is fairly simple and technical   var it works   false     post  some file php       function data          it works   true        alert it works     false  yes  that  alert  has to be here and not inside   post itself    What I want to achieve is   alert it works     true   Is there a way to do that  If not can   post   return a value to be applied to it works

User · Answer

AJAX stands for Asynchronous JavaScript and XML. Thus, the post to the server happens out-of-sync with the rest of the function. Try some code like this instead (it just breaks the shorthand $.post out into the longer $.ajax call and adds the async option).

var it_works = false;

$.ajax({
  type: 'POST',
  async: false,
  url: "some_file.php",
  data: "",
  success: function() {it_works = true;}
});

alert(it_works);

Hope this helps!

User · Answer

What you expect is the synchronous  blocking  type request   var it works   false   jQuery ajax     type   POST     url   some file php     success  function  data        it works   true          async  false     lt - this turns it into synchronous          Execution is BLOCKED until request finishes      it works is available alert it works     Requests are asynchronous  non-blocking  by default which means that the browser won t wait for them to be completed in order to continue its work  That s why your alert got wrong result   Now  with jQuery ajax you can optionally set the request to be synchronous  which means that the script will only continue to run after the request is finished     The RECOMMENDED way  however  is to refactor your code so that the data would be passed to a callback function as soon as the request is finished  This is preferred because blocking execution means blocking the UI which is unacceptable  Do it this way     post  some file php       function data        iDependOnMyParameter data        function iDependOnMyParameter param           You should do your work here that depends on the result of the request      alert param        All code here should be INDEPENDENT of the result of your AJAX request             Asynchronous programming is slightly more complicated because the consequence    of making a request is encapsulated in a function instead of following the request statement  But the realtime behavior that the user experiences can be significantly    better because they will not see a sluggish server or sluggish network cause the    browser to act as though it had crashed  Synchronous programming is disrespectful    and should not be employed in applications which are used by people    Douglas Crockford  YUI Blog

User · Answer

The reason your code fails is because post   will start an asynchronous request to the server  What that means for you is that post   returns immediately  not after the request completes  like you are expecting   What you need  then  is for the request to be synchronous and block the current thread until the request completes  Thus   var it works   false     ajax     url   some file php     async  false     makes request synchronous   success  function         it works   true           alert it works

User · Answer

It seems that your problem is simply a concurrency issue  The post function takes a callback argument to tell you when the post has been finished  You cannot make the alert in global scope like this and expect that the post has already been finished  You have to move it to the callback function

[javascript] JavaScript: Global variables after Ajax requests

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