node.js - Nodejs request handlers not waiting for function to return -

i have request handler particular route following:

function dothing(req, res) {     res.json({ "thing" : "thing", "otherthing": externalmodule.somefunction("yay"); }); } 

it seems result being send before "somefunction" call completes, "otherthing" json non-existent. how can wait function return data before sending response?

use callbacks. example:

externalmodule.somefunction = function(str, cb) {   // logic here ...    // ... execute callback when you're done,   // 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 });   }); }