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Wait until all jQuery Ajax requests are done?

Posted by: admin November 2, 2017 Leave a comment

Questions:

How do I make a function wait until all jQuery Ajax requests are done inside another function?

In short, I need to wait for all Ajax requests to be done before I execute the next. But how?

Answers:

jQuery now defines a ‘when’ function for this purpose.

http://api.jquery.com/jQuery.when/

It accepts any number of Deferred objects as arguments, and executes a function when all of them resolve.

That means, if you want to initiate (for example) four ajax requests, then perform an action when they are done, you could do something like this:

$.when(ajax1(), ajax2(), ajax3(), ajax4()).done(function(a1, a2, a3, a4){
    // the code here will be executed when all four ajax requests resolve.
    // a1, a2, a3 and a4 are lists of length 3 containing the response text,
    // status, and jqXHR object for each of the four ajax calls respectively.
});

function ajax1() {
    // NOTE:  This function must return the value 
    //        from calling the $.ajax() method.
    return $.ajax({
        url: "someUrl",
        dataType: "json",
        data:  yourJsonData,            
        ...
    });
}

In my opinion, it makes for a clean and clear syntax, and avoids involving any global variables such as ajaxStart and ajaxStop, which could have unwanted side effects as your page develops.

If you don’t know in advance how many ajax arguments you need to wait for (i.e. you want to use a variable number of arguments), it can still be done but is just a little bit trickier. See Pass in an array of Deferreds to $.when() (and maybe jQuery .when troubleshooting with variable number of arguments).

If you need deeper control over the failure modes of the ajax scripts etc., you can save the object returned by .when() – it’s a jQuery Promise object encompassing all of the original ajax queries. You can call .then() or .fail() on it to add detailed success/failure handlers.

Questions:
Answers:

If you want to wait until all ajax requests are finished in your document, no matter how many of them exists, just use $.ajaxStop event this way:

  $(document).ajaxStop(function () {
      // 0 === $.active
  });

In this case there is no need to guess how many requests can be in an application that might finish in the future. In some cases ajax requests can be part of a function’s inner logic, which can be quite complicated (e.g. calling other functions), and in that case you might not wait until said function is done with its entire logic rather than only waiting for the ajax part to complete.

$.ajaxStop here can also be bound to any html node that you think might be modified by ajax.

Again the purpose of this handler is to know when there is no active ajax not to clear or reset something.

Questions:
Answers:

I found a good answer by gnarf my self which is exactly what I was looking for 🙂

jQuery ajaxQueue

//This handles the queues    
(function($) {

  var ajaxQueue = $({});

  $.ajaxQueue = function(ajaxOpts) {

    var oldComplete = ajaxOpts.complete;

    ajaxQueue.queue(function(next) {

      ajaxOpts.complete = function() {
        if (oldComplete) oldComplete.apply(this, arguments);

        next();
      };

      $.ajax(ajaxOpts);
    });
  };

})(jQuery);

Then you can add a ajax request to the queue like this:

$.ajaxQueue({
        url: 'page.php',
        data: {id: 1},
        type: 'POST',
        success: function(data) {
            $('#status').html(data);
        }
    });

Questions:
Answers:

Use the ajaxStop event.

For example, let’s say you have a loading … message while fetching 100 ajax requests and you want to hide that message once loaded.

From the jQuery doc:

$("#loading").ajaxStop(function() {
  $(this).hide();
});

Do note that it will wait for all ajax requests being done on that page.

Questions:
Answers:

NOTE: The above answers use functionality that didn’t exist at the time that this answer was written. I recommend using jQuery.when() instead of these approaches, but I’m leaving the answer for historical purposes.

You could probably get by with a simple counting semaphore, although how you implement it would be dependent on your code. A simple example would be something like…

var semaphore  = 0,     // counting semaphore for ajax requests
    all_queued = false; // bool indicator to account for instances where the first request might finish before the second even starts

semaphore++;
$.get('ajax/test1.html', function(data) {
    semaphore--;
    if (all_queued && semaphore === 0) {
        // process your custom stuff here
    }
});

semaphore++;
$.get('ajax/test2.html', function(data) {
    semaphore--;
    if (all_queued && semaphore === 0) {
        // process your custom stuff here
    }
});

semaphore++;
$.get('ajax/test3.html', function(data) {
    semaphore--;
    if (all_queued && semaphore === 0) {
        // process your custom stuff here
    }
});

semaphore++;
$.get('ajax/test4.html', function(data) {
    semaphore--;
    if (all_queued && semaphore === 0) {
        // process your custom stuff here
    }
});

// now that all ajax requests are queued up, switch the bool to indicate it
all_queued = true;

If you wanted this to operate like {async: false} but you didn’t want to lock the browser, you could accomplish the same thing with a jQuery queue.

var $queue = $("<div/>");
$queue.queue(function(){
    $.get('ajax/test1.html', function(data) {
        $queue.dequeue();
    });
}).queue(function(){
    $.get('ajax/test2.html', function(data) {
        $queue.dequeue();
    });
}).queue(function(){
    $.get('ajax/test3.html', function(data) {
        $queue.dequeue();
    });
}).queue(function(){
    $.get('ajax/test4.html', function(data) {
        $queue.dequeue();
    });
});

Questions:
Answers:

jQuery allows you to specify if you want the ajax request to be asynchronous or not. You can simply make the ajax requests synchronous and then the rest of the code won’t execute until they return.

For example:

jQuery.ajax({ 
    async: false,
    //code
});

Questions:
Answers:

javascript is event-based, so you should never wait, rather set hooks/callbacks

You can probably just use the success/complete methods of jquery.ajax

Or you could use .ajaxComplete :

$('.log').ajaxComplete(function(e, xhr, settings) {
  if (settings.url == 'ajax/test.html') {
    $(this).text('Triggered ajaxComplete handler.');
    //and you can do whatever other processing here, including calling another function...
  }
});

though youy should post a pseudocode of how your(s) ajax request(s) is(are) called to be more precise…

Questions:
Answers:

A little workaround is something like this:

// Define how many Ajax calls must be done
var ajaxCalls = 3;
var counter = 0;
var ajaxCallComplete = function() {
    counter++;
    if( counter >= ajaxCalls ) {
            // When all ajax calls has been done
        // Do something like hide waiting images, or any else function call
        $('*').css('cursor', 'auto');
    }
};

var loadPersons = function() {
        // Show waiting image, or something else
    $('*').css('cursor', 'wait');

    var url = global.ctx + '/loadPersons';
    $.getJSON(url, function(data) {
            // Fun things
    })
    .complete(function() { **ajaxCallComplete();** });
};

var loadCountries = function() {
    // Do things
    var url = global.ctx + '/loadCountries';
    $.getJSON(url, function(data) {
            // Travels
    })
    .complete(function() { **ajaxCallComplete();** });
};

var loadCities = function() {
    // Do things
    var url = global.ctx + '/loadCities';
    $.getJSON(url, function(data) {
            // Travels
    })
    .complete(function() { **ajaxCallComplete();** });
};

$(document).ready(function(){
    loadPersons();
    loadCountries();
    loadCities();
});

Hope can be useful…

Questions:
Answers:

On the basis of @BBonifield answer, I wrote a utility function so that semaphore logic is not spread in all the ajax calls.

untilAjax is the utility function which invokes a callback function when all the ajaxCalls are completed.

ajaxObjs is a array of ajax setting objects [http://api.jquery.com/jQuery.ajax/].

fn is callback function

function untilAjax(ajaxObjs, fn) {
  if (!ajaxObjs || !fn) {
    return;
  }
  var ajaxCount = ajaxObjs.length,
    succ = null;

  for (var i = 0; i < ajaxObjs.length; i++) { //append logic to invoke callback function once all the ajax calls are completed, in success handler.
    succ = ajaxObjs[i]['success'];
    ajaxObjs[i]['success'] = function(data) { //modified success handler
      if (succ) {
        succ(data);
      }
      ajaxCount--;
      if (ajaxCount == 0) {
        fn(); //modify statement suitably if you want 'this' keyword to refer to another object
      }
    };
    $.ajax(ajaxObjs[i]); //make ajax call
    succ = null;
  };

Example: doSomething function uses untilAjax.

function doSomething() {
  // variable declarations
  untilAjax([{
    url: 'url2',
    dataType: 'json',
    success: function(data) {
      //do something with success data
    }
  }, {
    url: 'url1',
    dataType: 'json',
    success: function(data) {
      //do something with success data
    }
  }, {
    url: 'url2',
    dataType: 'json',
    success: function(response) {
      //do something with success data
    }
  }], function() {
    // logic after all the calls are completed.
  });
}

Questions:
Answers:

I highly recommend using $.when() if you’re starting from scratch.

Even though this question has over million answers, I still didn’t find anything useful for my case. Let’s say you have to deal with an existing codebase, already making some ajax calls and don’t want to introduce the complexity of promises and/or redo the whole thing.

We can easily take advantage of jQuery .data, .on and .trigger functions which have been a part of jQuery since forever.

Codepen

The good stuff about my solution is:

  • it’s obvious what the callback exactly depends on

  • the function triggerNowOrOnLoaded doesn’t care if the data has been already loaded or we’re still waiting for it

  • it’s super easy to plug it into an existing code

$(function() {

  // wait for posts to be loaded
  triggerNowOrOnLoaded("posts", function() {
    var $body = $("body");
    var posts = $body.data("posts");

    $body.append("<div>Posts: " + posts.length + "</div>");
  });


  // some ajax requests
  $.getJSON("https://jsonplaceholder.typicode.com/posts", function(data) {
    $("body").data("posts", data).trigger("posts");
  });

  // doesn't matter if the `triggerNowOrOnLoaded` is called after or before the actual requests 
  $.getJSON("https://jsonplaceholder.typicode.com/users", function(data) {
    $("body").data("users", data).trigger("users");
  });


  // wait for both types
  triggerNowOrOnLoaded(["posts", "users"], function() {
    var $body = $("body");
    var posts = $body.data("posts");
    var users = $body.data("users");

    $body.append("<div>Posts: " + posts.length + " and Users: " + users.length + "</div>");
  });

  // works even if everything has already loaded!
  setTimeout(function() {

    // triggers immediately since users have been already loaded
    triggerNowOrOnLoaded("users", function() {
      var $body = $("body");
      var users = $body.data("users");

      $body.append("<div>Delayed Users: " + users.length + "</div>");
    });

  }, 2000); // 2 seconds

});

// helper function
function triggerNowOrOnLoaded(types, callback) {
  types = $.isArray(types) ? types : [types];

  var $body = $("body");

  var waitForTypes = [];
  $.each(types, function(i, type) {

    if (typeof $body.data(type) === 'undefined') {
      waitForTypes.push(type);
    }
  });

  var isDataReady = waitForTypes.length === 0;
  if (isDataReady) {
    callback();
    return;
  }

  // wait for the last type and run this function again for the rest of the types
  var waitFor = waitForTypes.pop();
  $body.on(waitFor, function() {
    // remove event handler - we only want the stuff triggered once
    $body.off(waitFor);

    triggerNowOrOnLoaded(waitForTypes, callback);
  });
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<body>Hi!</body>

Questions:
Answers:

If you need something simple; once and done callback

        //multiple ajax calls above
        var callback = function () {
            if ($.active !== 0) {
                setTimeout(callback, '500');
                return;
            }
            //whatever you need to do here
            //...
        };
        callback();

Questions:
Answers:

I have met this problem and created a generic plugin jquery_counter to solve it:
https://bitbucket.org/stxnext/jquery_counter/

Questions:
Answers:

I found simple way, it using shift()

function waitReq(id)
{
  jQuery.ajax(
  {
    type: 'POST',
    url: ajaxurl,
    data:
    {
      "page": id
    },
    success: function(resp)
    {
      ...........
      // check array length if not "0" continue to use next array value
      if(ids.length)
      {
        waitReq(ids.shift()); // 2
      )
    },
    error: function(resp)
    {
      ....................
      if(ids.length)
      {
        waitReq(ids.shift());
      )
    }
  });
}

var ids = [1, 2, 3, 4, 5];    
// shift() = delete first array value (then print)
waitReq(ids.shift()); // print 1

Questions:
Answers:

Also you could use async.js.

I think its better than $.when because you can merge all kinds of asynchronous call that does not support promises out of the box like timeouts, SqlLite calls etc. and not just ajax requests.

Questions:
Answers:

My solution is as follows

var request;
...
'services': {
  'GetAddressBookData': function() {
    //This is the primary service that loads all addressbook records 
    request = $.ajax({
      type: "POST",
      url: "Default.aspx/GetAddressBook",
      contentType: "application/json;",
      dataType: "json"
    });
  },

  ...

  'apps': {
    'AddressBook': {
      'data': "",
      'Start': function() {
          ...services.GetAddressBookData();
          request.done(function(response) {
            trace("ajax successful");
            ..apps.AddressBook.data = response['d'];
            ...apps.AddressBook.Filter();
          });
          request.fail(function(xhr, textStatus, errorThrown) {
            trace("ajax failed - " + errorThrown);
          });

Worked quite nicely. I’ve tried a lot of different ways of doing this, but I found this to be the simplest and most reusable. Hope it helps

Questions:
Answers:

Look at my solution:

1.Insert this function (and variable) into your javascript file:

var runFunctionQueue_callback;

function runFunctionQueue(f, index, callback) {

  var next_index = index + 1

  if (callback !== undefined) runFunctionQueue_callback = callback;

  if (f[next_index] !== undefined) {
    console.log(index + ' Next function avalaible -> ' + next_index);
    $.ajax({
      type: 'GET',
      url: f[index].file,
      data: (f[index].data),
      complete: function() {
        runFunctionQueue(f, next_index);
      }
    });
  } else {
    console.log(index + ' Last function');
    $.ajax({
      type: 'GET',
      url: f[index].file,
      data: (f[index].data),
      async: false,
      complete: runFunctionQueue_callback
    });
  }
}

2.Buil an array with your requests, like this:

var f = [
           {file: 'file_path', data: {action: 'action', data: 'any_data}},
           {file: 'file_path', data: {action: 'action', data: 'any_data}},
           {file: 'file_path', data: {action: 'action', data: 'any_data}},
           {file: 'file_path', data: {action: 'action', data: 'any_data}}
        ];

3.Create callback function:

function Function_callback() {
  alert('done');
}

4.Call the runFunctionQueue function with parameters:

runFunctionQueue(f, 0, QuestionInsert_callback);
// first parameter: array with requests data
// second parameter: start from first request
// third parameter: the callback function

Questions:
Answers:

Solution given by Alex works fine. Same concept but using it a little different way (when number of calls is not known in advance)

http://garbageoverflow.blogspot.com/2014/02/wait-for-n-or-multiple-or-unknown.html

Questions:
Answers:

Try this way. make a loop inside java script function to wait until the ajax call finished.

function getLabelById(id)
{
    var label = '';
    var done = false;
    $.ajax({
       cache: false,
       url: "YourMvcActionUrl",
       type: "GET",
       dataType: "json",
       async: false,
       error: function (result) {
         label='undefined';
         done = true;
        },
       success: function (result) {
            label = result.Message;
            done = true;
        }
     });

   //A loop to check done if ajax call is done.
   while (!done)
   {
      setTimeout(function(){ },500); // take a sleep.
   }

    return label;
}