How can I return multiple function values in a single array

Question

I am crawling 5 different sites for data using node-fetch and cheerio. everything checks out but I need to collect the returned data from these 5 separate functions in an array.

First I store function name and url for each site in an object like so

    url: 'https://sampleurl.com',
    crawl: FirstLinkCrawl
}

const secondLink = {
    url: 'https://sampleurl.com',
    crawl: secondLinkCrawl
}
}```

Then I write the function to crawl each site like so, I ran this function with and without promise, both check out


```const secondLinkCrawl = (body) =>{
    return new Promise((res, rej)=>{
    "this crawl function is ran here, everything works fine, Data is an object"
        const error = false
        if(!error){
            res(Data)
        }else{
            rej()
        }
    })         
}```

This here is my fetch function that takes the url and a callback, which is the crawl function 

```async function Fetch(url, callback){
    const response = await fetch(url)
    const html = await response.text()
    callback(html)
}

Then I call the fetch and crawl using promise.all() in an attempt to have it return in an array, but in an array,

    const promises = [
     Fetch(firstLink.url, firstLink.crawl), 
     Fetch(secondLink.url, secondLink.crawl)]

    Promise.all(promises)
        .then(values => console.log(values))
        .catch(err => console.log(err))
}

When I run this, I get [ undefined, undefined ] But when I run it without promises and simply log the result, both of them run successfully. My aim is to get my results in a single array. what can I do?

I also tried declaring an array a the top of the page and then pushing each result into the array, after which I log the array at the bottom of the functions call. But the array returns empty

Abhay Sehgal · Accepted Answer · 2021-02-09 16:53:56Z

1

You're not returning anything from Fetch function that's why it's undefined. You can fix it by -

async function Fetch(url, callback){
    const response = await fetch(url)
    const html = await response.text()
    const result = await callback(html);
    return result;
}

As the callback, you are passing in Fetch function returns Promise so we can await it and return the result

answered Feb 9, 2021 at 16:53

Abhay Sehgal

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