Ramakrishna Reddy — whatsapp does not have a public API, hence you would not be able to find any documentation around it. The only API whatsapp has released for the public is “Click to chat”.
Essentially all this enables you to do is have a link clicking on which would send a custom message to a predefined number. Sure you can play around with it a little bit, but that’s about it.
For example: To create a link with just a pre-filled message, use https://api.whatsapp.com/send?text=urlencodedtext
What this will do is open up your contact list so that you can select contact(s) you wish to send this text to. This is what is used by ‘share on whatsapp’ plugins that you see on different websites.
Other than that, no real luck — not for the general public and typical businesses anyway.
Whatsapp does have APIs, that’s why you see businesses like KLM Airlines, Makemytrip, Oyo have things that can best be described as whatsapp transactional bots. But that is whatsapp experimenting with its marketplace and bot platform, for which it is collaborating with a select few partners who have a large enough transactional volume.
(All other solutions that you see on the internet are unofficial. They are workarounds and hacks. And as I mention in the story, can get your business in trouble on any given day.)
PS: If you are using ‘Whatsapp for business’, you will be having options to set up quick replies and things like that. But they are more like features of the product, so not really of contextual relevance here.