jQuery.when understanding

Ashish picture Ashish · Mar 12, 2011 · Viewed 92k times · Source

I am trying to use the jQuery.when to fire two ajax requests and then call some function after the two requests have completed. Here's my code:

var count = 0;
var dfr;

var showData = function(data) {
    dfr.resolve();
    alert(count);
   // Do something with my data data received
};

var method1 = function() {
    dfr = $.Deferred();

    return $.ajax('localhost/MyDataService/DataMethod_ReturnsData', {
        dataType: "jsonp",
        jsonp: "$callback",
        success: showData
    });
};

var method2 = function() {
    return $.ajax('localhost/MyDataService/DataMethod_ReturnsCount', {
        dataType: "jsonp",
        jsonp: "$callback",
        success: function(data) {
            count = data.d.__count;
        }
    });
};

$.when(method1(), method2())
    .then(showData());

However this is not working as expected. Ajax call in method1 will return data which is to be used in showData() and Ajax call in method2 will return count which is to be assigned to var count and later used in showData().

But when I fire the above code, method1 gets called and then method2 and then showData leaving the data in showData as 'undefined'. How can I achieve this via $.when which as far as I know proceeds only when both functions returning $.promise are executed. I want that both the ajax calls should be called in parallel and later results be displayed based on results from both calls.

Answer

Guillaume86 picture Guillaume86 · Mar 13, 2011
function showData(data1, data2) {
    alert(data1[0].max_id);
    alert(data2[0].max_id);
}

function method1() {
    return $.ajax("http://search.twitter.com/search.json", {
        data: {
            q: 'ashishnjain'
        },
        dataType: 'jsonp'
    });
}

function method2() {
    return $.ajax("http://search.twitter.com/search.json", {
        data: {
            q: 'ashishnjain'
        },
        dataType: 'jsonp'
    });
}

$.when(method1(), method2()).then(showData);​

Here's a working jsFiddle