Send messages to WhatsApp (web version only) programmatically.

whatsapp-sendMessage.js

function sendMessage(message){
  const mainEl = document.querySelector('#main')
  const textareaEl = mainEl.querySelector('div[contenteditable="true"]')

  if(!textareaEl) {
    throw new Error('There is no opened conversation')
  }

  textareaEl.focus()
  document.execCommand('insertText', false, message)
  textareaEl.dispatchEvent(new Event('change', { bubbles: true }))

  setTimeout(() => {
    (mainEl.querySelector('[data-testid="send"]') || mainEl.querySelector('[data-icon="send"]')).click()
  }, 100)
}

function sendMessage (message) {
  window.InputEvent = window.Event || window.InputEvent;

  var event = new InputEvent('input', {
    bubbles: true
  });

  var textbox = document.querySelector('div._3u328');

  textbox.textContent = message;
  textbox.dispatchEvent(event);

  document.querySelector("button._3M-N-").click();
}

Thank you @el3zahaby! It's now fixed.

Do you guys know internally (from whatsapp js) which function it calls?

there are unique values in the function ("div._3u328" and "button._3M-N-"). Whoever wanna use the function, has to update that. I did and I also upgraded that as an independent function from sessions

function sendMessage (message) {
  window.InputEvent = window.Event || window.InputEvent;

  var event = new InputEvent('input', {
    bubbles: true
  });

  var textbox = document.querySelector('[role="textbox"][data-tab="10"]');

  textbox.textContent = message;
  textbox.dispatchEvent(event);

  $('[data-testid="send"]').closest("button").click();
}

Thanks @semihkeskindev ! I just fixed it!