Almost every file uploader I found on web are expecting url to where we want to upload file. If you are using firebase storage then you will find this awkward as you don't have any rest url where you have to upload file.
Instead, file upload handled by firestore library firebase-storage.
After certain effort I found a way to use dropzone.js with firebase storage. Here is some snippet of code which you may find useful, If you are in the same situation as I am.
This both function are in same file