Great Dropbox tip:

If you have code on Dropbox, and are annoyed by node_modules sync ups (or just want to avoid syncing certain folders), there's a new way to solve your endless sync problems!

Dropbox has introduced a new attribute you could add to your files/folder to make sure they're ignored!

On Linux, you could simply create the following alias:
alias dignore="attr -s com.dropbox.ignored -V 1"
Then simply use your new dignore command like so:
dignore path_to_file_or_folder

Important: make sure no active sync is running for the folder, as it could cause "Ignored Item Conflict"
More info on Dropbox Ignore

Dropbox Ignore VS Exclude

Dropbox Ignore - when you don't want Dropbox to upload a certain file/folder to the Dropbox Cloud. Dropbox Exclude - when you don't want Dropbox to download a certain file/folder to your local machine.

That's pretty much it!