Como fazer alguém te responder no whatsapp

comoSerChatoNowhatsapp.js

var counter = 0;

var mensagens = document.getElementsByClassName("message-in");
var quantidadeMsg = mensagens.length

var i = setInterval(function(){
  window.InputEvent = window.Event || window.InputEvent;
	var d = new Date();
	var event = new InputEvent('input', {bubbles: true});
  var textbox = document.querySelector('#main > footer > div.block-compose > div.input-container > div.pluggable-input.pluggable-input-compose > div.pluggable-input-body.copyable-text.selectable-text');
	textbox.textContent = "Me responde!";
	textbox.dispatchEvent(event);
	document.querySelector("button.compose-btn-send").click();
  counter++;

  console.log("Já enviei " + counter +  ' mensagens.')

  if(quantidadeMsg != mensagens.length)
		clearInterval(i);
}, 1000);