jQuery callback for multiple ajax calls

Question

I want to make three ajax calls in a click event  Each ajax call does a distinct operation and returns back data that is needed for a final callback  The calls themselves are not dependent on one another  they can all go at the same time  however I would like to have a final callback when all three are complete       button   click function         fun1        fun2        fun3      now do something else when the requests have done their  success  callbacks       var fun1   function           ajax    code          var fun2    function           ajax    code          var fun3    function           ajax    code

User · Answer

Not seeing the need for any object malarky myself  Simple have a variable which is an integer  When you start a request  increment the number  When one completes  decrement it  When it s zero  there are no requests in progress  so you re done       button   click function         var inProgress   0       function handleBefore             inProgress                function handleComplete             if   --inProgress                   do what s in here when all requests have completed                          ajax           beforeSend  handleBefore          complete  function                     whatever             handleComplete                   whatever                         ajax           beforeSend  handleBefore          complete  function                     whatever             handleComplete                   whatever                         ajax           beforeSend  handleBefore          complete  function                     whatever             handleComplete                   whatever

User · Answer

I came across this problem today  and this was my naive attempt before watching the accepted answer    lt script gt      function main             var a  b  c         var one   function                 if   a    undefined   amp  amp  b    undefined  amp  amp  c    undefined                     alert  Ok                 else                   alert                                            fakeAjaxCall  function                 a    two              one                       fakeAjaxCall  function                 b    three              one                       fakeAjaxCall  function                 c    four              one                         function fakeAjaxCall  a             a             main    lt  script gt

User · Answer

ajax  type  POST   url  www naver com   dataType  text   async false      complete function xhr  textStatus         error function xhr  textStatus         success function  data              ajax  type  POST                                                  success function data                     ajax  type  POST                                                                                       I m sorry but I can t explain what I worte cuz I m a Korean who can t speak even a word in english  but I think you can easily understand it

User · Answer

async     false    By default  all requests are sent asynchronously  i e  this is set to true by default   If you need synchronous requests  set this option to false  Cross-domain requests and dataType   jsonp  requests do not support synchronous operation  Note that synchronous requests may temporarily lock the browser  disabling any actions while the request is active  As of jQuery 1 8  the use of async  false with jqXHR    Deferred  is deprecated  you must use the success error complete callback options instead of the corresponding methods of the jqXHR object such as jqXHR done   or the deprecated jqXHR success

User · Answer

I asked the same question a while ago and got a couple of good answers here  Best way to add a   39 callback  39  after a series of asynchronous XHR calls

User · Answer

It s not jquery  and it appears jquery has a workable solution  but just as another option      I ve had similar problems working heavily with SharePoint web services - you often need to pull data from multiple sources to generate input for a single process   To solve it I embedded this kind of functionality into my AJAX abstraction library  You can easily define a request which will trigger a set of handlers when complete  However each request can be defined with multiple http calls  Here s the component  and detailed documentation    DPAJAX at DepressedPress com  This simple example creates one request with three calls and then passes that information  in the call order  to a single handler          The handler function  function AddUp Nums    alert Nums 1    Nums 2    Nums 3               Create the pool  myPool   DP AJAX createPool             Create the request  myRequest   DP AJAX createRequest AddUp            Add the calls to the request  myRequest addCall  GET    http   www mysite com Add htm    5 10     myRequest addCall  GET    http   www mysite com Add htm    4 6     myRequest addCall  GET    http   www mysite com Add htm    7 13             Add the request to the pool  myPool addRequest myRequest      Note that unlike many of the other solutions  including  I believe the  when  solution in jquery  provided this method does not force single threading of the calls being made - each will still run as quickly  or as slowly  as the environment allows but the single handler will only be called when all are complete  It also supports the setting of timeout values and retry attempts if your service is a little flakey   I ve found it insanely useful  and incredibly simple to understand from a code perspective    No more chaining  no more counting calls and saving output   Just  set it and forget it

User · Answer

Looks like you ve got some answers to this  however I think there is something worth mentioning here that will greatly simplify your code   jQuery introduced the   when in v1 5   It looks like     when   ajax         ajax       then function  resp1  resp2          this callback will be fired once all ajax calls have finished        Didn t see it mentioned here  hope it helps

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It s worth noting that since   when expects all of the ajax requests as sequential arguments  not an array  you ll commonly see   when used with  apply   like so     Save all requests in an array of jqXHR objects var requests   arrayOfThings map function thing        return   ajax           method   GET           url   thing     thing id                when apply this  requests  then function resp1  resp2                     Each argument is an array with the following structure    data  statusText  jqXHR       var responseArgsArray   Array prototype slice call this  arguments         Using the Spread syntax  you can now write this code like so    when    requests  then     responses    gt           do something with responses     This is because   when accepts args like this   when ajaxRequest1  ajaxRequest2  ajaxRequest3    And not like this    when  ajaxRequest1  ajaxRequest2  ajaxRequest3

User · Answer

I got some good hints from the answers on this page  I adapted it a bit for my use and thought I could share      lets say we have 2 ajax functions that needs to be  synchronized       In other words  we want to know when both are completed  function foo1 callback          ajax           url    echo html            success  function data                alert  foo1                callback                                        function foo2 callback          ajax           url    echo html            success  function data                alert  foo2                callback                            here is my simplified solution ajaxSynchronizer   function         var funcs           var funcsCompleted   0      var callback       this add   function f            funcs push f              this synchronizer   function             funcsCompleted            if  funcsCompleted    funcs length                callback call this                        this callWhenFinished   function cb            callback   cb          for  var i   0  i  lt  funcs length  i                  funcs i  call this  this synchronizer                         this is the function that is called when both ajax calls are completed  afterFunction   function         alert  All done           this is how you set it up var synchronizer   new ajaxSynchronizer    synchronizer add foo1   synchronizer add foo2   synchronizer callWhenFinished afterFunction     There are some limitations here  but for my case it was ok  I also found that for more advanced stuff it there is also a AOP plugin  for jQuery  that might be useful  http   code google com p jquery-aop

User · Answer

I found an easier way to do it without the need of extra methods that arrange a queue   JS    ajax     type   POST     url   ajax1 php     data       id  1      cb  method1   declaration of callback method of ajax1 php        success  function data       catching up values   var data   JSON parse data     var cb data 0  cb   here whe catching up the callback  method1    eval cb   JSON stringify data        here we calling method1 and pass all data             ajax     type   POST     url   ajax2 php     data       id  2      cb  method2   declaration of callback method of ajax2 php        success  function data       catching up values   var data   JSON parse data     var cb data 0  cb   here whe catching up the callback  method2    eval cb   JSON stringify data        here we calling method2 and pass all data             the callback methods function method1 data     here we have our data from ajax1 php alert  method1 called with data   data     doing stuff we would only do in method1         function method2 data     here we have our data from ajax2 php alert  method2 called with data   data     doing stuff we would only do in method2          PHP  ajax1 php    lt  php       catch up callbackmethod      cb   POST  cb     is  method1        json     array       cb    gt   cb       value    gt   ajax1                      encoding array in JSON format     echo json encode  json     gt    PHP  ajax2 php    lt  php       catch up callbackmethod      cb   POST  cb     is  method2        json     array       cb    gt   cb       value    gt   ajax2                      encoding array in JSON format     echo json encode  json     gt

User · Answer

Here is a callback object I wrote where you can either set a single callback to fire once all complete or let each have their own callback and fire them all once all complete   NOTICE  Since jQuery 1 5  you can use the deferred method as described in another answer       when   ajax           then function results              Example of deferred here  for jQuery  lt  1 5 the following will work or if you need to have your ajax calls fired at unknown times as shown here with two buttons  fired after both buttons are clicked   usage   for single callback once complete  Working Example     initialize here var requestCallback   new MyRequestsCompleted       numRequest  3      singleCallback  function            alert   I m the callback                 usage in request   ajax       url    echo html        success  function data            requestCallback requestComplete true               ajax       url    echo html        success  function data            requestCallback requestComplete true               ajax       url    echo html        success  function data            requestCallback requestComplete true               each having their own callback when all complete  Working Example    initialize  var requestCallback   new MyRequestsCompleted       numRequest  3        usage in request   ajax       url    echo html        success  function data            requestCallback addCallbackToQueue true  function                 alert  Im the first callback                            ajax       url    echo html        success  function data            requestCallback addCallbackToQueue true  function                 alert  Im the second callback                            ajax       url    echo html        success  function data            requestCallback addCallbackToQueue true  function                 alert  Im the third callback                             The Code   var MyRequestsCompleted    function         var numRequestToComplete  requestsCompleted  callBacks  singleCallBack       return function options            if   options  options                numRequestToComplete   options numRequest    0          requestsCompleted   options requestsCompleted    0          callBacks               var fireCallbacks   function                 alert  we re all complete                for  var i   0  i  lt  callBacks length  i    callBacks i                        if  options singleCallback  callBacks push options singleCallback            this addCallbackToQueue   function isComplete  callback                if  isComplete  requestsCompleted                if  callback  callBacks push callback               if  requestsCompleted    numRequestToComplete  fireCallbacks                       this requestComplete   function isComplete                if  isComplete  requestsCompleted                if  requestsCompleted    numRequestToComplete  fireCallbacks                       this setCallback   function callback                callBacks push callBack

User · Answer

I like hvgotcodes  idea  My suggestion is to add a generic incrementer that compares the number complete to the number needed and then runs the final callback  This could be built into the final callback   var sync      callbacksToComplete   3   callbacksCompleted   0   addCallbackInstance   function      this callbacksCompleted      if callbacksCompleted    callbacksToComplete       doFinalCallBack                 Edited to reflect name updates

User · Answer

EDIT -- perhaps the best option would be to create a service endpoint that does everything the three requests do   That way you only have to do one request  and all the data is where you need it to be in the response   If you find you are doing the same 3 requests over and over again  you will probably want to go this route   It is often a good design decision to set up  a facade service on the server that lumps commonly used smaller server actions together   Just an idea     one way to do it would be to create a  sync  object in your click handler before the ajax calls   Something like  var sync        count  0     The sync will be bound to the scope of the success calls automatically  closure    In the success handler  you increment the count  and if it is 3 you can call the other function   Alternatively  you could do something like  var sync        success1Complete  false            success3Complete  false      when each success is executed  it would change the value in the sync to true   You would have to check the sync to make sure that all three are true before proceeding   Note the case where one of your xhrs does not return success -- you need to account for that   Yet another option would be to always call the final function in your success handlers  and have it access the sync option to determine whether to actually do anything   You would need to make sure the sync is in the scope of that function though

User · Answer

Ok  this is old but please let me contribute my solution     function sync  callback        syncCount--      if   syncCount  lt  1   callback      function allFinished                      window syncCount   2     ajax       url   url       success  function data            sync  allFinished              someFunctionWithCallback  function    sync  allFinished          It works also with functions that have a callback  You set the syncCount and you call the function sync      in the callback of every action

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