How to cancel abort jQuery AJAX request

Question

I ve an AJAX request which will be made every 5 seconds  But the problem is before the AJAX request if the previous request is not completed I ve to abort that request and make a new request   My code is something like this  how to resolve this issue     document  ready      var fn   function              ajax               url   ajax progress ftl               success  function data                      do something                                       var interval   setInterval fn  500

User · Answer

When you make a request to a server  have it check to see if a progress is not null  or fetching that data  first  If it is fetching data  abort the previous request and initiate the new one   var progress   null  function fn              if  progress            progress abort              progress     ajax  ajax progress ftl             success  function data                  do something             progress   null

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jQuery  Use this as a starting point - as inspiration  I solved it like this    this is not a perfect solution  it just aborts the last instance and is WIP code   var singleAjax   function singleAjax constructor url  params           remember last jQuery s get request     if  this lastInstance            this lastInstance abort        triggers  always   and  fail           this lastInstance   false                how to use Deferred   http   api jquery com category deferred-object      var  def   new   Deferred            pass the deferrer s request handlers into the get response handlers     this lastInstance     get url  params           fail  def reject             triggers  always   and  fail            success  def resolve         triggers  always   and  done           return the deferrer s  control object   the promise object     return  def promise           initiate first call singleAjax   ajax php    a  1  b  2        always function a b c   console  amp  amp  console log a b c          second call kills first one singleAjax   ajax php    a  1  b  2        always function a b c   console  amp  amp  console log a b c             here you might use  always    fail    success   etc

User · Answer

You can use jquery-validate js   The following is the code snippet from jquery-validate js      ajax mode  abort    usage    ajax   mode   abort    port   uniqueport         if mode  abort  is used  the previous request on that port  port can be undefined  is aborted via XMLHttpRequest abort    var pendingRequests           ajax     Use a prefilter if available  1 5   if     ajaxPrefilter           ajaxPrefilter function  settings     xhr             var port   settings port          if   settings mode      abort                  if   pendingRequests port                      pendingRequests port  abort                              pendingRequests port    xhr                      else          Proxy ajax     ajax     ajax        ajax   function  settings             var mode      mode  in settings   settings     ajaxSettings   mode              port      port  in settings   settings     ajaxSettings   port          if   mode      abort                  if   pendingRequests port                      pendingRequests port  abort                              pendingRequests port    ajax apply this  arguments               return pendingRequests port                     return ajax apply this  arguments              So that you just only need to set the parameter mode to abort when you are making ajax request   Ref https   cdnjs cloudflare com ajax libs jquery-validate 1 14 0 jquery validate js

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Create a function to call your API  Within this function we define request callApiRequest     get     - even though this is a definition of a variable  the request is called immediately  but now we have the request defined as a variable  Before the request is called  we check if our variable is defined typeof callApiRequest      undefined  and also if it is pending suggestCategoryRequest state       pending  - if both are true  we  abort   the request which will prevent the success callback from running      We need to wrap the call in a function callApi   function             check if request is defined  and status pending     if  typeof callApiRequest      undefined           amp  amp  suggestCategoryRequest state       pending                abort request         callApiRequest abort                 define and make request     callApiRequest     get  https   example com   function  data             data   JSON parse data     optional  for JSON data format            success callback              Your server API might not support aborting the request  what if API executed some code already    but the javascript callback will not fire  This is useful  when for example you are providing input suggestions to a user  such as hashtags input    You can further extend this function by adding definition of error callback - what should happen if request was aborted    Common use-case for this snippet would be a text input that fires on keypress event  You can use a timeout  to prevent sending  some of  requests that you will have to cancel  abort

User · Answer

Why should you abort the request   If each request takes more than five seconds  what will happen   You shouldn t abort the request if the parameter passing with the request is not changing  eg - the request is for retrieving the notification data   In such situations  The nice approach is that set a new request only after completing the previous Ajax request     document  ready       var fn   function               ajax               url   ajax progress ftl               success  function data                      do something                             complete  function   setTimeout fn  500                             var interval   setTimeout fn  500

User · Answer

You should also check for readyState 0  Because when you use xhr abort   this function set readyState to 0 in this object  and your if check will be always true -  readyState   4     document  ready      var xhr       var fn   function            if xhr  amp  amp  xhr readyState    4  amp  amp  xhr readyState    0               xhr abort                      xhr     ajax               url   ajax progress ftl               success  function data                      do something                                       var interval   setInterval fn  500

User · Answer

I know this might be a little late but i experience similar issues where calling the abort method didnt really aborted the request  instead the browser was still waiting for a response that it never uses  this code resolved that issue    try           xhr onreadystatechange   null          xhr abort      catch  e

User · Answer

The jquery ajax method returns a XMLHttpRequest object  You can use this object to cancel the request   The XMLHttpRequest has a abort method  which cancels the request  but if the request has already been sent to the server then the server will process the request even if we abort the request but the client will not wait for handle the response   The xhr object also contains a readyState which contains the state of the request UNSENT-0  OPENED-1  HEADERS RECEIVED-2  LOADING-3 and DONE-4   we can use this to check whether the previous request was completed     document  ready      var xhr       var fn   function            if xhr  amp  amp  xhr readyState    4               xhr abort                      xhr     ajax               url   ajax progress ftl               success  function data                      do something                                       var interval   setInterval fn  500

[ajax] How to cancel/abort jQuery AJAX request?

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