How to make sure the query executed before render() on Node JS

Question

I don't know whether it is async problem so that sometimes the result had no product data but only type data. However, sometimes it will have both data.

My setup: Node JS, Express, Mongoose

router.get('/', function (req, res, next) {
var data = {};
Product.find().limit(4).populate({path: 'region_id', model: Region})
    .then(function (doc) {
        data.product = doc;
    });
Type.find()
    .then(function (doc) {
        data.type = doc;
    });

res.render('index', {title: 'Home', items: data});
});

If I am correct then how to make sure all the find() function is executed before running render().

Thanks!

Answer 1

Because both asynchronous operations return Promise s, you should use Promise.all , which will resolve when both complete. There's no need for an outer data object, just use the values of the resolved promises directly. Also, don't forget to handle errors with catch when using Promises:

router.get('/', function (req, res, next) {
  Promise.all([
    Product.find().limit(4).populate({path: 'region_id', model: Region}),
    Type.find()
  ])
    .then(([product, type]) => {
      res.render('index', {title: 'Home', items: { product, type } });
    });
    .catch((err) => {
      // handle errors
    });
});