Wait until function is complete and then render the page - node.js

Question

I have a function which scrapes an element and return the element value. This is the code of reale-scraper.js:
module.exports.RealeScraper = function() {
return new Promise((res, rej) => {
var url = 'example.com';
var compagnia;
//Start Puppeteer and scrape element
ptr.launch().then(async browser => {
const page = await browser.newPage();
await page.setViewport({ width: 1280, height: 800 });
await page.goto(url, {waitUntil: "networkidle0"});
await page.type('input[name="username"]', config.utente);
await page.type('input[name="password"]', config.pass);
await Promise.all([
page.click('input[type="SUBMIT"]'),
page.waitForNavigation({waitUntil: 'networkidle2'})
]);
await page.waitForSelector('#tableSceltaProfilo > tbody > tr:nth-child(1) > td:nth-child(2)');
const element = await page.$("#tableSceltaProfilo > tbody > tr:nth-child(1) > td:nth-child(2)");
compagnia = await page.evaluate(element => element.textContent, element);
await page.screenshot({path: 'screenshot.png'});
await browser.close();
});
res(compagnia);
});
}
Then i call that function and try to send data to my ejs template in home.js:
var scraper = require('../scrapers/reale-scraper');
router.get('/home', function(req, res, next) {
RealeScraper().then((compagnia) => {
res.render('nuovo-sinistro', {
titolo: 'Manager Perizie',
compagnia: compagnia
});
}).catch((error) => {
console.log(error);
});
});
I want to wait until 'RealeScraper' is finished and returned me a value so that I can pass it to res.render. I've tried using Promise but it doesn't work. It gives me no errors but when I load the page, the function doesn't start and so is rendered without the variable.
I've also tried different methods but ended up having the page loading forever.
Any help would be really appreciated, thanks!

Answer 1

You call //Start Puppeteer and scrape element and res(compagnia); at the same time, while compagnia is empty, it has been returned.
Just call res when scrape element finished.
...
await browser.close();
res(compagnia);
...
I think it will be better if you only use async\await like this:
module.exports.RealeScraper = async function () {
var url = 'example.com';
var compagnia;
//Start Puppeteer and scrape element
let browser = await ptr.launch();
const page = await browser.newPage();
await page.setViewport({ width: 1280, height: 800 });
await page.goto(url, { waitUntil: "networkidle0" });
await page.type('input[name="username"]', config.utente);
await page.type('input[name="password"]', config.pass);
await page.click('input[type="SUBMIT"]'); // why you do that in parallel?
await page.waitForNavigation({ waitUntil: 'networkidle2' });
await page.waitForSelector('#tableSceltaProfilo > tbody > tr:nth-child(1) > td:nth-child(2)');
const element = await page.$("#tableSceltaProfilo > tbody > tr:nth-child(1) > td:nth-child(2)");
compagnia = await page.evaluate(element => element.textContent, element);
await page.screenshot({ path: 'screenshot.png' });
await browser.close();
return compagnia;
}
// ...
var scraper = require('../scrapers/reale-scraper');
router.get('/home', async function (req, res, next) {
try {
let compagnia = await RealeScraper();
res.render('nuovo-sinistro', {
titolo: 'Manager Perizie',
compagnia: compagnia
});
} catch (error) {
console.log(error);
}
});