Question

I have a small function to validate the user input. In that function I will also check if the email address is already taken. But I have some trouble with the async callback.
I hope anyone could give me a hint, how I could solve this. I use nodejs with the express 3 framework, mongodb and the node-validator library.

This is a part of my validation function:

function check(data, callback) {
    mongoose.model('User', User).count(data, function (err, count) {
        callback(err, !! count);
    });
};

function validate(email, password, confirm) {
    var v = new Validator(),
        errors = new Array();

    v.error = function (msg) {
        errors.push(msg);
    };

    check({email: email}, function (err, exists) {
        v.check(exists, { email: 'E-Mail is already taken' }).equals(false);
    });
    ...
    return errors;
}

Based on the async callback the variable errors is at the return statement empty. How could I else check if the email address is already in the databse?

Answer 1

You need to think async and pass callbacks that will be called asynchronously.
Quick example:

app.get('/blah', function(req, res) {
   // Whatever
   validate(email, pass, confirm, function(errors) {
     if (errors.length == 0)
         resp.send(200, 'blah');
     else
         resp.send(400, 'blah blah');
   });
})

function validate(email, password, confirm, callback) {
    var v = new Validator(),
        errors = new Array();

    v.error = function (msg) {
        errors.push(msg);
    };

    check({email: email}, function (err, exists) {
        v.check(exists, { email: 'E-Mail is already taken' }).equals(false);
    }, function() {
        callback(errors);
    });
    // ...
    return errors;
}