Constructing a JavaScript object from two AJAX requests

Question

I have an API for getting an array of objects that represent Boats and it returns an "id", "name", "length" and "harbour_id" for each boat.

I also have another API for getting the "harbour_name" from "harbour_id". While writing AJAX requests for both is not a problem, the thing that puzzles me is this: I have to construct an array of objects where every boat contains all the data for itsef, "harbour_name" included.

How do I do it?

Let's write some code:

var boats;
function getBoats() {
    $.ajax({
    url:'/',
    type:'GET',
    success: gotBoats,
    error: didntGetBoats,
    });
}

function gotBoats(data, textStatus, jqXHR) {
    boats = $.parseJSON(data);
        // I presume I need to make another request somewhere around here
        // but I'm not sure how to do it to bind the response data to
        // the correct boat
}

function didntGetBoats(jqXHR, textStatus, errorThrown) {
    alert(errorThrown);
}

After this problem is solved, I also need to be able to do it backwards - input a new boat and post it's location to a proper place and the rest of the data to it's proper place.

Thanks in advance for tips :)

T.J. Crowder · Accepted Answer · 2014-05-31 10:11:17Z

You're not going to have to one more request, you'll have to do a request for each boat, which will be really inefficient. If there's any way to get the harbour name included in the first response, that's what you want to do.

But if you can't, you can fire off the series of requests for the boats:

function gotBoats(data, textStatus, jqXHR) {
    // Somethign to keep track of how many harbour name responses we've seen
    var harbourNameCount = 0;

    // Get the boats. (Do you need that parseJSON call? jQuery will
    // do it automatically if the Content-Type of the response is correct;
    // or you can add `dataType: 'json'` to the `ajax` call.)
    boats = $.parseJSON(data);

    // Loop through requesting harbour names
    $.each(boats, function(i, boat) {
        // Ask for this harbour name, using ES5's Function#bind to
        // pass the relevant boat into the callbacks. You'll need
        // a shim for Function#bind on IE8 and earlier.
        $.ajax({
            url:      "/path/to/harbour/name/query",
            data:     {harbour_id: boat.harbour_id},
            success:  gotHarbour.bind(null, boat),
            error:    didntGetHarbour.bind(null, boat),
            complete: finishHarbour
        });
    });

    // Callback for when we get the name; note that since we use this
    // with bind, the boat is our first argument.
    function gotHarbour(boat, data) {
        boat.harbour_name = data.harbour_name;
    }

    // Callback for when we don't get the name for some reason
    function didntGetHarbour(boat) {
        boat.harbour_name = "(Unknown: " + boat.harbour_id + ")";
    }

    // Called after the two callbacks above
    function finishHarbour() {
        // Count this response
        ++harbourNameCount;

        // If we have seen all the responses, we're done!
        if (harbourNameCount === boats.length) {
            allFinishedLoading();
        }
    }
}

Excelent, this was what I was missing :) I'm aware that I'll need to do multiple requests and I'm afraid the API is as-is :-/ However, thank you very much, now I can get back on track.

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