What about https://web.whatsapp.com/

[jaydipsinh8]

First let me thanks for this button.
Second this isn't actually a issue.This work fine for me mobile devic(Android & Ios).Now i am little curious can i share data on https://web.whatsapp.com/ using this button directly/with littel chages.
if someone use whatsapp whatsapp-web then what we have to do to send this massage on https://web.whatsapp.com/.

[kriskbx]

Sorry, this is not possible at the moment. WhatsApp is a closed system and there are only a few interfaces developers can use, like the url-scheme or Androids intent system.

[evandroamparo]

Now there is a WhatsApp API to start a chat. See https://www.whatsapp.com/faq/en/general/26000030.
I tested in Chrome desktop and the link opens WhatsApp Web. It doesn't work in Opera. In Android, it opens the installed app.
I'll make a fork to use the new API.