How to ensure async function returns value before continuing

Question

I have looked at this question/answer but can't get it to work for my needs.

I have an async function in an offer.js file, which I need to call from a Controller file. The offer.js file works correctly and returns JSON data. It's the calling Controller file which I can't get to 'wait' for the data to come back before continuing with the rest of the page.

This is what the Controller file does:

var router = require('express').Router(); // Express.js router functionality
const Offer = require('../models/offer'); // the offer.js file which has getAllOffers() async function

// call/return the data from getAllOffers() async function
var rsOffersAll = async function() {
  return await Offer.getAllOffers(); 
}

// I would like rsOffersAll to have data before doing anything further at this point.

// if the homepage, supply the rsOffersAll data to the view.
router.get('/', function(req, res, next) {
  res.render('index', { data: rsOffersAll  });  // the data needs to be here. this should not run until the data is available to pass to the view
});

How do I ensure that var rsOffersAll has data before the router.get... stuff executes?

router.get('/', async function(...) { ... { data: await rsOffersAll () }); ...}); — blex
– blex, Commented Nov 17, 2019 at 20:44

James · Accepted Answer · 2019-11-17 20:46:12Z

3

rsOffersAll is redundant here, you await the result internally but you don't then await the result of rsOffersAll from the route handler.

router.get('/', async (req, res, next) => {
  const data = await Offers.getAllOffers();
  res.render('index', { data });
});

answered Nov 17, 2019 at 20:46

James

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9 Comments

volume one Over a year ago

thanks for this. but what if I want to do this res.render('index', { pagetitle: 'Homepage', metadesc: 'The site's homepage', data: rsOffersAll }); where I want to pass more parameters to the view than just the data ?

blex Over a year ago

@volumeone just add them: { pagetitle: 'Homepage', /* ... */, data } (but just keep data, don't do data: rsOffersAll) Just having data is equivalent to having data: data.

James Over a year ago

@volumeone as blex has already explained, I've simply made use of short-hand notation, if you need more properties then you simply add them like you would normally

volume one Over a year ago

if I do this

router.get('/', async (req, res, next) => {   const data = await Offers.getAllOffers(); console.dir(data);   res.render('index', { data }); });

How come data never prints to the console?

James Over a year ago

@volumeone yes, you would appear to be opening a global connection and not closing therefore when another request comes in it hangs

|

Saurabh Yadav · Accepted Answer · 2019-11-17 20:49:30Z

0

rsOffersAll is async and it will return a promise so you can use then

 router.get('/', function(req, res, next) {

    rsOffersAll().then((res) = >{
        res.render('index', { data: res  });
    });

});

edited Nov 17, 2019 at 20:49

answered Nov 17, 2019 at 20:47

Saurabh Yadav

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3 Comments

James Over a year ago

I wouldnt recommend mixing Promises & async / await

Saurabh Yadav Over a year ago

@James can you explain the little bit reason for this ?

James Over a year ago

are you saying you agree with me but don't understand why? 🤔

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