Mongoose query skipped over

Question

I have a function in NodeJS that makes a query into Mongo. The function is "checkForMatchingEmail".

var result = checkForMatchingEmail(req.body.email);

if ( result === 1) { // something something }
else if ( result === 0) { // something something }

I want to use the RESULT variable for deciding on what to do next. (sending a response to the front-end whether such an e-mail exists in DB).

The problem is that the query to Mongo seems to lag a bit, so the thread just skips over it and the if/else tree is useless, because the query results are not in yet.

What to do?

EDIT:

checkForMatchingEmail looks like this:

function checkForMatchingEmail(email) {
    var result = 0;

    User.findOne({email: email}, function(err,obj) {
        console.log("email is " + email);

        if (err) {
            return handleError(err);
        } else if (obj != null) {
            console.log("This email already exists." + obj);
            result = 1;
        } else if (obj === null) {
            result = 0;
            console.log("This email does not exist.");
        }
    });

    return result;
}

See http://stackoverflow.com/questions/23667086/why-is-my-variable-unaltered-after-i-modify-it-inside-of-a-function-asynchron — JohnnyHK, Aug 14 '14 at 13:14

saintedlama · Answer 1 · 2014-08-14T13:18:06.417

First of all node.js is asynchronous and evented. There are no threads in this context that could skip over.

When querying mongodb via mongoose you're using a model let's assume User to execute a query. A typical mongoose query looks something like this

User.find({ email : 'someone@example.com'}, function(err, user) {
  if (err) {
    // Do something with the err
  }

  // Here you have your query result
});

Taking your code example you should extend checkForMatchingEmail with a callback argument in which you process the result

checkForMatchingEmail(req.body.email, function(result) {
  if ( result === 1) { // something something }
  else if ( result === 0) { // something something }
});

You might read What is Node.js chapter in Mixu's Node book that explains asynchronous execution in node.js quite well.

Mongoose query skipped over

1 Answers1