jQuery Handle fallback for failed AJAX Request

Question

Can jQuery provide a fallback for failed AJAX calls  This is my try   function update         var requestOK   false         getJSON url  function            alert  request successful            requestOK   true               if   requestOK            alert  request failed              Unfortunately  even if the callback function of the   getJSON   method is called  i get the message  request failed   before the callback function has the opportunity to set the requestOK variable  I think it s because the code runs in parallel  Is there a way to handle such situations  I thought about chaining or some way of waiting for the AJAX request  including its callback function  But how  Does anyone know how to do that

User · Accepted Answer

You will need to either use the lower level $.ajax call, or the ajaxError function. Here it is with the $.ajax method:

function update() {
  $.ajax({
    type: 'GET',
    dataType: 'json',
    url: url,
    timeout: 5000,
    success: function(data, textStatus ){
       alert('request successful');
    },
    fail: function(xhr, textStatus, errorThrown){
       alert('request failed');
    }
  });
}

EDIT I added a timeout to the $.ajax call and set it to five seconds.

User · Answer

Dougs answer is correct  but you actually can use   getJSON and catch errors  not having to use   ajax   Just chain the getJSON call with a call to the fail function     getJSON   foo bar json        done function     alert  request successful            fail function     alert  request failed          Live demo  http   jsfiddle net NLDYf 5   This behavior is part of the jQuery Deferred interface  Basically it allows you to attach events to an asynchronous action after you call that action  which means you don t have to pass the event function to the action   Read more about jQuery Deferred here  http   api jquery com category deferred-object

User · Answer

I believe that what you are looking for is error option for the jquery ajax object   getJSON is a wrapper to the   ajax object  but it doesn t provide you with access to the error option   EDIT  dcneiner has given a good example of the code you would need to use   Even before I could post my reply

User · Answer

I prefer to this approach because you can return the promise and use  then successFunction  failFunction   anywhere you need to   var promise     ajax       type   GET       dataType   json       url  url      timeout  5000      then function  data  textStatus  jqXHR         alert  request successful         function  jqXHR  textStatus  errorThrown         alert  request failed           also access the success and fail using variable promise then successFunction  failFunction

User · Answer

Yes  it s built in to jQuery   See the docs at jquery documentation   ajaxError may be what you want

[jquery] jQuery: Handle fallback for failed AJAX Request

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