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javascriptjquerycallbackpromise
Regis Portalez
Regis Portalez

Reputation: 4845

jQuery ajax : perform a data treatment before callback

I'm writing a library to access data from a server, and return formatted data to the consumer of my functions. Here is an example of what I'd like to have: 

// my code
var model = function () {
    return $.ajax(myRequest).done(function (rawData) {
        return treatment(data);
    });
}

// client code
var useModel = function () {
    var modelPromise = model();
    modelPromise.done(function (formattedData) { // consume this result })
}

where formattedData is the result of my first done callback and not the rawData.

Do you have any ideas?

Thanks

R.

Upvotes: 0

Views: 284

Answers (2)

blong
blong

Reputation: 2713

Regis,

I like Beetroot's answer a lot. Here's an example I made while trying to understand this concept for myself: Multiple asynchronous requests with jQuery .

Source from jsFiddle:

var logIt = function (msg) {
    console.log(((new Date()).toLocaleTimeString()) + ": " + msg);
}, pauseBrowser = function (ms) {
    ms += new Date().getTime();
    while (new Date() < ms) {}
}, dataForService1 = {
    json: JSON.stringify({
        serviceNumber: 1,
        description: "Service #1's data",
        pauseAfterward: 3 // for pausing the client-side
    }),
    delay: 0 // delay on the server-side
}, dataForService2 = {
    json: JSON.stringify({
        serviceNumber: 2,
        description: "Service #2's data",
        pauseAfterward: 1
    }),
    delay: 0 // delay on the server-side
};

function getAjaxConfiguration() {
    return {
        type: 'POST',
        url: '/echo/json/',
        success: function (data) {
            var msg = "Handling service #" + data.serviceNumber + "'s success";
            logIt(msg);
            logIt(JSON.stringify(data));
        }
    };
}

var async2 = function () {
    var ajaxConfig = $.extend(getAjaxConfiguration(), {
        data: dataForService2
    });
    return $.ajax(ajaxConfig);
};

var async1 = function () {
    var ajaxConfig = $.extend(getAjaxConfiguration(), {
        data: dataForService1
    });
    return $.ajax(ajaxConfig);
};

var do2AsynchronousFunctions = function () {
    var dfd = new $.Deferred();

    async1()
    .then(function (async1ResponseData) {
        logIt("async1's then() method called, waiting " + async1ResponseData.pauseAfterward + " seconds");
        pauseBrowser(async1ResponseData.pauseAfterward * 1000);
    })
    .done(function (a1d) {
        logIt("async1's done() method was called");
        return async2()
        .then(function (async2ResponseData) {
            logIt("async2's then() method called, waiting " + async2ResponseData.pauseAfterward + " seconds");
            pauseBrowser(async2ResponseData.pauseAfterward * 1000);
        })
        .done(function (a2d) {
            logIt("async2's done() method was called");
            dfd.resolve("final return value");
        });
    });

    return dfd.promise();
};

$.when(do2AsynchronousFunctions()).done(function (retVal) {
    logIt('Everything is now done! Final return value: ' + JSON.stringify(retVal));
});

Upvotes: 0

Beetroot-Beetroot
Beetroot-Beetroot

Reputation: 18078

Regis,

jQuery's documention for .then() says :

As of jQuery 1.8, the deferred.then() method returns a new promise that can filter the status and values of a deferred through a function, replacing the now-deprecated deferred.pipe() method.

The second example for .then() is similar to what you want (though not involving ajax).

As far as I can tell, the necessary changes to your code are very minimal :

// my code
var model = function () {
    return $.ajax(myRequest).then(function (rawData) {
        return treatment(rawData);
    });
}

// client code
var useModel = function () {
    var modelPromise = model();
    modelPromise.done(function (formattedData) { // consume this result })
}

Upvotes: 1

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