AngularJS and async calls

Question

I'm an AngularJS promises novice and getting really frustrated on how to implement it. I'm hoping somebody here can help me out.

I have the following client-side code:

// Pass result to ng-csv directive.
$scope.generateEmployeeData = function () {
        $scope.employeename = empName;
        $http.get('/api/employee-information/download').then(function (data) {
            console.log(data);
            return data;
        }).catch(function (err) {
            ToastFactory.error({
                title: "Oops!",
                text: "Something went wrong while downloading employee data.",
                icon: "exclamation-sign"
            });
        });
    }

... and the ff. server-side code:

// Download Employee data (.../api/employee-information/download)
exports.downloadEmployee = function (req, res) {
    var tempCtr = [];

    var dlPromise = EmployeeInfo.find({}, function (err, results) {
        var tempCtr = [];
        if (err) { return err; }

        console.log("dlpromise in");
        return results;
    });

    q.all(dlPromise)
        .then(function (results) {
            _.forEach(results, function (item) {
                tempCtr.push({
                    employeeID: item.employeeID,
                    employeeName: item.employeeName
                });
            });
        });

    console.log("tempctr out");
    console.log(tempCtr);

    return res.json(tempCtr);
}

When I checked my logs, I saw that console.log("tempctr out") was called first before console.log("dlpromise in"), and I get that it's because the process is asynchronous. That's why I used q.all (based on this SO answer), because I thought that it would resolve dlPromise first before going inside then(). But it didn't work. What am I missing? Is my understanding of AngularJS' promises skewed in general?

I've been trying to solve this for a long time without any success. Please help.

Thank you.

UPDATE: I added a console.log after console.log("dlpromise in");. This is the result:

dlpromise in
[ { _id: 58c7b885db0afd48ee427a73,
    employeeID: '12349876',
    employeeName: 'Tester'}]

What does the api return? It looks like you are downloading something, what content type are you sending the response with? — Marcus Höglund
– Marcus Höglund, Commented Mar 17, 2017 at 14:12
console.log("tempctr out"); is not into the .then(), see this link about promises: pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html — Groben
– Groben, Commented Mar 17, 2017 at 14:33
@Groben Thank you for the link. This line definitely hit home: "Many of us are using promises without really understanding them." Will definitely read this. — Dee J.
– Dee J., Commented Mar 17, 2017 at 15:17

Arg0n · Accepted Answer · 2017-03-17 14:35:06Z

1

I'm not really familiar with the server-side code, but I'm assuming it's NodeJS?

I think you could change the code to something in the lines of this (assuming res.json(tempCtr) sends the response data):

exports.downloadEmployee = function (req, res) {
    EmployeeInfo.find({}, function (err, results) {
        var tempCtr = [];
        if (err) { return err; }

        _.forEach(results, function (item) {
            tempCtr.push({
                employeeID: item.employeeID,
                employeeName: item.employeeName
            });
        });

        console.log("tempctr out");
        console.log(tempCtr);
        res.json(tempCtr);
    });
}

answered Mar 17, 2017 at 14:35

Arg0n

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4 Comments

Dee J. Over a year ago

Yep, it's node.js. This was what I tried earlier. What happened was it called tempctr out first before going back to do the _.forEach function. Client-side controller got an empty response.

Arg0n Over a year ago

Using this code tempctr out should not run before _.forEach, I can't say if the response is empty though. Did you try it?

Dee J. Over a year ago

I see, I'll give it another shot. :)

Dee J. Over a year ago

Finally it worked! Now I don't get why q didn't work in this case...but anyway. Thank you so much! :)

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