Async function returning empty value then doing operations?

Question

Hey I have written this code in node js

async function getUdemydata(){

    try{
        var finalData = []
        const res = await axios.get(baseUrl)
        const $ = cheerio.load(res.data);

        $('div[class="content"]').each(async (i,el) =>{
            const courseTitle = $(el).find("a").text()
            const aa = $(el).html() 
            const courseUrl = await getCoupenCode($(el).find("a").attr("href"))
            const courseDescription = $(el).find(".description").text().trim()
            const courseImage = await formateImageUrl($(el).find(".image").html())
            var dataObj = {
            "title": courseTitle,
            "description": courseDescription,
            "image": courseImage,
            "link": courseUrl
            }
            finalData.push(dataObj);
            console.log('appended');
        })
        return (finalData);
    } catch(error){
        console.error(error);
    }

}

(async()=>{
    var rs = await getUdemydata();
    console.log(rs);
})()

When I call the getUdemydata() function only the empty array is printed after that appended which is inside the function is being printed what should I change in the code so that the function will return the final array

spender · Accepted Answer · 2022-01-28 18:57:09Z

2

The definition of .each is as follows:

each<T>(fn: (i: number, el: T) => boolean | void): Cheerio<T>

It is not Promise-aware, so does not await the async function you supply as its parameter.

Remember that an async function is just a normal function that returns a Promise, so you could map these function calls, ending up with an array of Promise, then wait for them all.

// var finalArray = [] // <-- NO
const promises = $('div[class="content"]')
    .toArray()
    .map(async (el,i) => {
        // same body as `each` in your code
        // except, don't push into `finalArray`
        // just return your value

        // finalData.push(dataObj); // <-- NO
        return dataObj;
    });
const finalArray = await Promise.all(promises);

or if the parallelism of running all those promises at once is too much, then the documentation suggests that a Cheerio is Iterable, so just loop over $('div[class="content"]') with a normal

for(const el of $('div[class="content"]')) { //...

edited Jan 28, 2022 at 18:57

answered Jan 28, 2022 at 18:35

spender

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2 Comments

spender Over a year ago

...as an aside, bearing in mind that every other higher-order function over arrays tends to call its selector with index as the 2nd parameter, the parameter-order of .each(index, element) bucks the trend in a "set-you-up-to-fail" kind of way

spender Over a year ago

@AnishGowda I made an edit to the code because it is not necessary to push items into finalArray

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