How do I convert "YANG" data model to "JSON"? 
As there is many many docs available in web, in that they changed in YANG
synatx to JSON but how the value for the leaf or leaf list they are getting? from where and how it will get actual data in JSON from YANG?
Yang is a modeling language, not a data generation language.
What you are asking for is a simulator that will contain the same or pseudo logic as your application to generate data.
how to convert YANG data model to JSON data?