node.js fs.exists() will be deprecated, what to use instead?

Use fs.existsSync().

fs.existsSync() has not been deprecated.

https://nodejs.org/api/fs.html#fs_fs_existssync_path

fs.existsSync(path)

Added in: v0.1.21
path |
Synchronous version of fs.exists(). Returns true if the file exists, false otherwise.

Note that fs.exists() is deprecated, but fs.existsSync() is not. (The callback >parameter to fs.exists() accepts parameters that are inconsistent with other >Node.js callbacks. fs.existsSync() does not use a callback.)