How do I check if a mobile number is on WhatsApp or not with programming?

I wanted to build a web-based system using which you will come to know whether the mobile number is registered with WhatsApp or not? It's just to check whether the number entered in textbox have WhatsApp account or not? I tried finding resources regarding the same but unable to get any solution on it, please share some link for reference so, I can implement it and get to the final result.