detect change of status in textbox web.whatssap

Question

I am trying through javascript code to activate the send button in the web.whatsapp chat 1.- when the text is empty, a microphone icon simply appears 2.- when you enter a text, change the icon to a send button This happens when you write something and some event is fired that detects the change and activates the submit button I just want to replicate this

my code example :

window.InputEvent = window.Event || window.InputEvent;
var event = new InputEvent('input', {bubbles: true});
document.querySelector('#main > footer > div._2BU3P.tm2tP.copyable-area > div > span:nth-child(2) > div > div._2lMWa > div.p3_M1 > div > div.fd365im1.to2l77zo.bbv8nyr4.mwp4sxku.gfz4du6o.ag5g9lrv > p').textContent = "prueba";
document.querySelector('#main > footer > div._2BU3P.tm2tP.copyable-area > div > span:nth-child(2) > div > div._2lMWa > div.p3_M1 > div > div.fd365im1.to2l77zo.bbv8nyr4.mwp4sxku.gfz4du6o.ag5g9lrv > p')
textbox.dispatchEvent(event);

window.InputEvent = window.Event || window.InputEvent;
var event = new InputEvent('input', {bubbles: true});
document.querySelector('#main > footer > div._2BU3P.tm2tP.copyable-area > div > span:nth-child(2) > div > div._2lMWa > div.p3_M1 > div > div.fd365im1.to2l77zo.bbv8nyr4.mwp4sxku.gfz4du6o.ag5g9lrv > p').textContent = "prueba";
document.querySelector('#main > footer > div._2BU3P.tm2tP.copyable-area > div > span:nth-child(2) > div > div._2lMWa > div.p3_M1 > div > div.fd365im1.to2l77zo.bbv8nyr4.mwp4sxku.gfz4du6o.ag5g9lrv > p')
textbox.dispatchEvent(event);