Chain ajax and execute it in sequence. Jquery Deferred

Question

I have 3 processes that needs ajax to complete. But it is asynchronous and it fails to do what I wanted to do..

Lets say:

function a(param1, param2)         


        

Answer 1

You can chain asynchronous calls like ajax calls using jQuery's deferred object and using 'then'.

You can also change it to use functions that returns a deferred promise object, instead of an ajax call as I have in my example.

http://jsfiddle.net/q4cFv/

(Example with async function: http://jsfiddle.net/q4cFv/1/)

$(function() {
    var delay = 3,
        span = $('span'),
        posts = [
            {
                input1: 'My name 1',
                input2: 'My address 1',
                input3: 'My country 1'
            },
            {
                input1: 'My name 2',
                input2: 'My address 2',
                input3: 'My country 2'
            },
            {
                input1: 'My name 3',
                input2: 'My address 3',
                input3: 'My country 3'
            },
            {
                input1: 'My name 4',
                input2: 'My address 4',
                input3: 'My country 4'
            }
        ],
        looper = $.Deferred().resolve();

    $.each(posts, function(i, data) {
        looper = looper.then(function() {
            return $.ajax({
                data: {
                    json: JSON.stringify(data),
                    delay: delay
                },
                method: 'post',
                url: '/echo/json/',
                dataType: 'json'
            }).done(function(response) {
                span.append('Response:
');
                for(key in response) {
                    span.append(key + ': ' + response[key] + '
');
                }
                $('span').append('Waiting ' + delay + ' seconds

');
            });
        });
    });
});