Skip to content
Advertisement

NodeJS: How to fill Array through callback function

I hope the following code snippet is enough to explain my problem:

function getChildrensRoomsProductNumbers(uuids, callback) {
        var productNumbers = [];
        uuids.forEach(uuid => getProductNumber(uuid, function(productNumber){
            productNumbers.push(productNumber);}))
        callback(productNumbers);
    }

So for an array of uuids, I’d like to request the corresponding product numbers from an online shop and store them in the array productNumbers which then I’d like to pass to a parent function for further manipulation through calling callback(productNumbers)

The request itself is done in the getProductNumber function.

However, I don’t understand why the array productNumbers is empty? I know forEach is not returning anything so that’s why I prepared an array beforehand that should be filled in my idea.

I’m relatively new to NodeJS/JavaScript, so I probably might be missing some basic concepts here.

This is the getProductNumber function:

function getProductNumber(uuid, callback){
    getToken(function(err, token){
        var headers = {
            'Authorization': 'Bearer ' + token,
            'Content-Type': 'application/json',
        };
        const options = {
            url: BASE_URL + 'api/product/' + uuid,
            method: 'GET',
            headers: headers
        };

        axios.request(options)
            .then(res => {
                console.log("NUmber: " + res.data.data.productNumber);
                callback(res.data.data.productNumber);
            })
            .catch(err => {
                console.error(err.response);
            });
        })
}

Advertisement

Answer

please first learn async/await style to get rid of callbacks

then this will be doable :

    async function getChildrensRoomsProductNumbers(uuids) {
        var productNumbers = [];
        for (let uuid of uuids) {
            const productNumber = await getProductNumber(uuid);
            productNumbers.push(productNumber);
        }
        return productNumbers;
    }

like people said in comments getProductNumber looks like it does an async job. if you wat to stick with callbacks you can use https://www.npmjs.com/package/async to fire a callback when your loop is done.

Advertisement