Nodejs request handlers not waiting for function to return

Question

Nodejs request handlers not waiting for function to return

I have a request handler for a particular route that does something like the following:

function doThing(req, res) {
    res.json({ "thing" : "thing", "otherThing": externalModule.someFunction("yay"); });
}

It seems like the result is being send before the "someFunction" call completes, so the "otherThing" JSON is always non-existent. How can I wait for that function to return data before sending a response?

node.js

Answer 1

Use callbacks. Example:

externalModule.someFunction = function(str, cb) {
  // your logic here ...

  // ... then execute the callback when you're finally done,
  // with error argument first if applicable
  cb(null, str + str);
};

// ...

function doThing(req, res, next) {
  externalModule.someFunction("yay", function(err, result) {
    if (err) return next(err);
    res.json({ "thing" : "thing", "otherThing": result });
  });
}