How to delete and write a file in an application using js?

Question

JavaScript

There is such a problem. I need to delete a file using js, for example, in the data folder, despite the fact that this js file is next to the data folder, and then download the file from the site and place it in the data folder.
I found the file api, but did not understand what was there and how, for some reason the browser does not want to do anything.
Note: this app is for android (suddenly needed).

Answer 1

www.html5rocks.com/en/tutorials/file/filesystem