I am trying to send text- messages on WhatsApp with javascript?

I am trying to send text messages on whatsapp web version on chrome. (www.web.whatsapp.com)

This is the code:

document.getElementsByClassName("input")[1].innerHTML="This message was written via JS script! ";

var input = document.getElementsByClassName("icon btn-icon icon-send");
input[0].click();

But the problem is , initially when no text is present the input box looks like this:

And only when I physically write some text it changes to this:

And only now my script works since it requires the Send text button.

I tried Jquery code to simulate keypresses at $('.input)by following function:

function pressKey() {
  var e = jQuery.Event("keypress");
  e.which = 32; // # space
  $(".input").trigger(e)[1];
  e.which = 91;
  $(".input").trigger(e)[1];
  e.which = 32; // # space
  $(".input").trigger(e)[1];
  e.which = 32; // # space
  $(".input").trigger(e)[1];

}

It didn't work.

How can I get the Send text button by script?

Here is the screen recording :