async method always returning undefined

Question

I can't solve that problem so I'm asking that here:

This is the async function, and as you can see is returning an array. But it returns an undefined value.

async function scrape(pageURL) {
var dealArray = [];
try {
    const browser = await puppeteer.launch({ headless: true });
    const page = await browser.newPage();
    await page.goto(pageURL);
    await page.waitForSelector('div.s-item-container');
    const dealsElements = await page.$$('div.s-item-container');
    for(deal of dealsElements) {
        let dealTitleElement = await deal.$('div.s-item-container a.s-access-detail-page');
        let dealTitleValue = await (await dealTitleElement.getProperty('title')).jsonValue();
        let dealPriceElement= await deal.$('div.s-item-container span.a-color-price');
        let dealPriceValue = await (await dealPriceElement.getProperty('textContent')).jsonValue();
        let dealReviewsElement = await deal.$('div.s-item-container .a-icon-star');
        let dealLinkValue = await (await dealTitleElement.getProperty('href')).jsonValue() + '&tag=dragonstv-21';
        let dealReviewsClass = await (await dealReviewsElement.getProperty('className')).jsonValue();
        let dealReviewsValue;
        if(dealReviewsClass) {
            let starValue = dealReviewsClass.substring(26);
                if(starValue.indexOf('-') === -1) {
                    dealReviewsValue = starValue;
                } else {
                    let stars = starValue.replace('-', '.');
                    dealReviewsValue = stars;
                }
        }
        dealArray.push({
            "title": dealTitleValue,
            "price": dealPriceValue,
            "reviews": dealReviewsValue + "/5.0",
            "link": dealLinkValue,
            "store": "Amazon",
        });
    }
    return Promise.resolve(dealArray);
} catch(e) {
    console.error('Error: ' + e);
}
}

And here is how I'm calling it:

scrape('working link').then((data) => {
    console.log(data) // result: undefined
}

It works only if I declare the variable out of the function and the function doesn't return anything but only changes the array content.

Note that because your function is declared with the async keyword, you don't need to explicitly return a promise with return Promise.resolve(dealArray). You can simply return dealArray and it will be wrapped in a promise due to the async keyword. — chharvey
– chharvey, Commented Jan 11, 2019 at 22:11

Elliot Nelson · Accepted Answer · 2019-01-03 13:54:24Z

1

As written, your function must return an array (empty or otherwise). If it's returning undefined, then you're generating an exception and should see one in the console, via your catch statement. If you're not seeing it, you might try removing the try/catch and see what exception bubbles up.

answered Jan 3, 2019 at 13:54

Elliot Nelson

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1 Comment

Alessandro Bertozzi Over a year ago

Seems like the last iteration gives a null value. I'm going to solve it myself.

Alessandro Bertozzi · Accepted Answer · 2019-01-12 20:17:15Z

0

I've actually figured the problem out. It was returning a string so I had to use JSON.parse(request) so I have an object on which I can work on.

answered Jan 12, 2019 at 20:17

Alessandro Bertozzi

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