Question

For the reading a table script shown below, I am trying to run the query in the parameter and for each result trying to append a value from a different table to the result. But due to asynchronous nature of azure, request.respond() is always called before getInvites. Which means that the results are never appended with invites.

function read(query, user, request) {

    request.execute({
        success: function (results) {
            for (var i = 0; i < results.length; i++) {
                getInvites(results[i].id, function (invites) {
                    console.log("Assigning results.invites"); //runs second
                    results[i].invites = invites;
                });
            }
            console.log("Request Responding"); //runs first
            request.respond();
        }
    });

}

function getInvites(id, cb) {
    var InvitesTable = tables.getTable("Invites").where({
        "PlanID": id
    }).select("UserID", "Attending");
    InvitesTable.read({
        success: function (results) {
            if (cb) cb(results);
        }
    });
}

This is a followup question from this as I am unable to use external libraries in Azure. So how can I workaround the problem?

Answer 1

The asynchronous nature of the operations makes that a little challenging. What you need to do is to only call request.respond() once all the operations are done. I really miss the await keyword which I’m so fond from C#, but I’ve used an “asynchronous for loop” before, and it’s worked quite well. Your code would look something like the one shown below:

function read(query, user, request) {
    request.execute({
        success: function (results) {
            var index = 0;
            var executeStep = function() {
                if (index === results.length) {
                    // all invites have been retrieved
                    console.log("Request Responding");
                    request.respond();
                } else {
                    getInvites(results[index].id, function(invites) {
                        console.log('Assigning results.invites');
                        results[i].invites = invites;
                        index++;
                        executeStep();
                    });
                }
            }

            executeStep();
        }
    });
}

function getInvites(id, cb) {
    var InvitesTable = tables.getTable("Invites").where({
        "PlanID": id
    }).select("UserID", "Attending");
    InvitesTable.read({
        success: function (results) {
            if (cb) cb(results);
        }
    });
}