Has anyone done that before?
Usually that’s done by uploading a csv that contains the records, but upload button doesn’t support csv files and I have no idea how to read files’ contents???
That’s great but is there a way to read this data from user by reading an uploaded file?
Users can’t upload CSV files, you are right, it is only the admin of the website that can import CSV files into a dataset.
https://support.wix.com/en/article/importing-data-to-a-database-collection
File Limitations
https://support.wix.com/en/article/supported-media-file-types-and-file-sizes
File Limitations Through Upload Button (Wix Forms)
https://support.wix.com/en/article/importing-data-to-a-database-collection
A plausible option for you would be to let users upload their .xls or .xlsx files and you simply change them to csv files so that you can import them yourself.
You could add this file to a separate dataset and then use code to bulk insert them into your existing dataset which holds all your records.
You can even do it like this tutorial if you convert the csv files to JSON.
https://support.wix.com/en/article/corvid-tutorial-importing-and-exporting-collection-data-with-code
Also, with the above tutorial you can actually use it on your published site, however it still has to be you as Admin or your dataset permissions have to set open to anyone.
Using the form on your published site
There is no way of getting this users uploaded document put straight into a dataset as it is saved into your Media Manager.
If you were using Wix Stores for example, there are automated ways that the admin can import a csv file to a dataset so that you don;t need to do each record manually.
https://support.wix.com/en/article/importing-products-to-wix-stores
https://www.wix.com/corvid/forum/community-feature-request/csv-import-export-1/p-4
https://ds0089.wixsite.com/code