Sharing Config between Node.js, React.js and Python Apps
I’d recommend using TOML. It’s supported by all major languages and allows the use of comments which JSON does not.
My project currently involves several components using either Javascript and Python 

Node.js server
Python flask API server
Python data processing scripts (numpy, pandas, etc)
React.js web client
React Native mobile client

These components share several common config values such as a database connection URI string postgresql://admin:password@localhost:5432/foobar used by server-side components and the API server url https://api.example.com/v1 used by client-side components.
Question: Is there a best practice for sharing config files across components that uses different languages? 
For example, 

Should all components (server and client side) access the same config file? If so, which format should it be in, JSON, YAML, etc? 
Should all components share a common config file (where only common config values are stored in), but also have a second config file specific to that component?
Should all server side components share the same config file, while client side components have their own individual config files?

Thank you for your advices :)