Cannot get the result of an async function in controller - node.js

Question

This is my controller:
const rssService = require('../services/rss.service');
async function parser() {
const result = await rssService.rssParser('someurl');
return result;
};
const parse = async function (req, res) {
const p = new Promise((resolve, reject) => {
const t = parser();
if (t === undefined) {
resolve(t);
} else {
// eslint-disable-next-line prefer-promise-reject-errors
reject('something bad happened');
}
});
p.then((result) => res.send(result)).catch((message) => console.log(`ERROR ${message}`));
};
module.exports = {
parse,
};
in the function : parser() above, I am trying to call my rss.service.js file which I have the logic. This file is a rss parser which tries to parse the feed and do some calculations (which needs promises and async) and then return the json object.
Here is how my rss.service look :
const rssParser = async function parseRssFeed(url) {
const parser = new Parser();
const appRoot = process.env.PWD;
const downloadDir = `${appRoot}/downloads/`;
if (!fs.existsSync(downloadDir)) {
fs.mkdirSync(downloadDir);
}
try {
const feed = await parser.parseURL('someurl');
const processedFeedItems = await Promise.all(feed.items.map(async (currentItem) => {
const {
fileUrl,
downloadPath,
} = await downloadFile(currentItem);
const hashValue = calculateHash(downloadPath)
return {
title: currentItem.title,
hash: hashValue,
url: mp3FileUrl,
};
}));
return (JSON.stringify(processedFeedItems));
} catch (error) {
console.error(error);
return 'error';
}
};
when I debug my code I can verify that Json object has been created with correct data, but the result does not return to the callee(controller).

Answer 1

I'll go in a little deeper since you mentioned you're new:
const rssService = require('../services/rss.service');
// This is an async function (always returns a promise)
async function parser() {
const result = await rssService.rssParser('someurl');
return result;
};
const parse = async function (req, res, next) {
// In await/async, you should use try/catch/throw instead of .then and .catch
// It does the same thing, but it's the preferred syntax and is "easier" to read IMO
// Out in "the community" people will complain if you mix await/async with promises like that
try {
// Adding await to ensure left-assign works.
// This is necessary because parser is an async function (so returns a promise)
const result = await parser();
// here, since you used `await` you get the value instead of the promise
if (result === undefined) throw new Error('something bad happened')
return res.send(result)
} catch (error) {
console.log(`ERROR ${error.message}`;
// Do you need to do anything else with this error? I assume something like:
return next(error);
}
};
module.exports = {
parse,
};

Answer 2

In a fast look, It seems you have forgot to wait for resolve the parser promise.
...
const p = new Promise(async(resolve, reject) => {
const t = await parser();
...