How to read and write a file in JavaScript?

Question

JavaScript

The *.csv format file must be read and the information written into it again. Actions take place in the browser.

Answer 1

You can read the file through FileApi - but the user must explicitly give you the file
. There is no write to the file, but it may appear in the future, at least in the drafts of the FileApi standard there are already outlines.
You can try to make a crutch, through data-uri + download-link
In general, file manipulation is the prerogative of the server