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?

Answer 1

Yes, it's built in to jQuery. See the docs at jquery documentation.

ajaxError may be what you want.

Answer 2

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');
    },
    error: function(xhr, textStatus, errorThrown){
       alert('request failed');
    }
  });
}

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

Answer 3

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)