How to store response data into an array out of the current function in node js?

How do i store all result data into pImages array i am getting the result but in that case i think async function will work but i dont know how to apply it. please help, my code is

exports.addImage = (req, res, next) => {
    let imageArray = req.files.productImageArray;

    if (!req.files || Object.keys(req.files).length === 0) {
        return res.status(400).send("No files were uploaded.");
    }
    
    // here all images will be stored in array format
        let pImages = [];

         for (let f in imageArray) {
            imagekit.upload(
                {
                    file: imageArray[f].data, //required
                    fileName: imageArray[f].name, //required
                    customMetadata: {
                        color: req.body.productLabels[f],
                        default: req.body.defaultProduct[f]
                    }
                },
                function(error, result) {
                    if (error) console.log(error);
                    else {
                        console.log(result)
                        pImages.push(result)
                    }
                }
            );
        }

    console.log("p", pImages); //output p []
   
};

Thanks in Advance

You could wrap imagekit.upload(...) in a promise and then await this promise.

Therefore your promise has to be resolved or rejected in the callback on imagekit.upload.

Be aware that your addImage method now has to be async to use the await keyword and therefor returns a promise itself.

exports.addImage = async (req, res, next) => {
    let imageArray = req.files.productImageArray;

    if (!req.files || Object.keys(req.files).length === 0) {
        return res.status(400).send("No files were uploaded.");
    }
    
    // here all images will be stored in array format
        let pImages = [];

         for (let f in imageArray) {
            try{
                const pImage = await new Promise((resolve,reject)=>{
                    imagekit.upload(
                        {
                            file: imageArray[f].data, //required
                            fileName: imageArray[f].name, //required
                            customMetadata: {
                                color: req.body.productLabels[f],
                                default: req.body.defaultProduct[f]
                            }
                        },
                        function(error, result) {
                            if (error){
                                reject(error);
                            } else {
                                resolve(result)
                            }
                        }
                    );
                });
                pImages.push(pImage);
            } catch(e){
                console.error(e);
            }
        }

    console.log("p", pImages); //output p []
   
};

There are other things in your code i haven't addressed.

In the first line you are accessing req.files.productImageArray without checking if req.files is defined. This check is done afterwords. So you should move your first line after this check.

Is req.files.productImageArray an array like the name says? If so you shouldn't use a for in loop use a for of loop instead and in your sanity checks you should include Array.isArray(req.files.productImageArray).