Express JS page rendered before async function was executed - node.js

Question

I have a problem with express.js routing. I want to get all restaurants when users open /restaurant/map. Problem is that function gm.geocode is async so page is rendered before that function is executed. How would I get variabile mapsData at the right time, so when page /restaurant/map is loaded? What is the right way to do that?
var express = require('express');
var router = express.Router();
var gm = require('googlemaps');
var fs=require('fs');
var staticDB=require('./staticDB.js');
var mapsData=[];
/* GET home page. */
router.get('/', function (req, res, next) {
//not important
});
router.get('/map/', function (req, res, next) {
var counter=0;
console.log('Request URL:', req.originalUrl);
for (i = 0; i < staticDB.addresses.addresses.length; i++) {
gm.geocode(staticDB.addresses.addresses[i].street + ", " + staticDB.addresses.addresses[i].city, function (err, data){
mapsData.push({
"name": staticDB.restaurants.restaurants[counter].name,
"location": data.results[0].geometry.location
});
counter++;
}, false);
}
res.render('map', {
title: 'title',
restaurants: mapsData
});
});
module.exports = router;

Answer 1

Never use regular for loops to deal with asynchronous flows. There are modules that handle those scenarios for you, like async, or even promises. In your case, your code should look like this, using async.each (I didn't test it):
router.get('/map/', function (req, res, next) {
var counter=0;
console.log('Request URL:', req.originalUrl);
async.each(staticDB.addresses.addresses, function (address, cb) {
gm.geocode(address.street + ", " + address.city, function (err, data){
mapsData.push({
"name": staticDB.restaurants.restaurants[counter].name,
"location": data.results[0].geometry.location
});
counter++;
cb();
}, false);
}, function (err) {
if (err) {
return res.render('error', { error: err });
}
res.render('map', {
title: 'title',
restaurants: mapsData
});
});
});