How to fill message box on Whatsapp Web?

I’m trying to send a message on Whatsapp Web (https://web.whatsapp.com/) only using Javascript, for study purposes.

Here is the DIV that has the message box :

<div class="fd365im1 to2l77zo bbv8nyr4 mwp4sxku gfz4du6o ag5g9lrv" contenteditable="true" role="textbox" spellcheck="true" title="Type a message" data-tab="10" data-lexical-editor="true" style="user-select: text; white-space: pre-wrap; word-break: break-word;"><p class="selectable-text copyable-text"><br></p></div>

And here is my code :

document.getElementsByClassName('fd365im1 to2l77zo bbv8nyr4 mwp4sxku gfz4du6o ag5g9lrv')[0].innerText = 'My message content';

The code runs without errors, but the message field is not filled, nothing happens on the interface. This code used to run before, but not anymore.

What am i missing ? You can try your self accessing the whatsapp web and using Chrome devtools.

Answer

you can use

update*

// wait until paste all text
function waitForPastedData(elem, old) {
  if (elem.childNodes && elem.childNodes.length == old) {
    return true
  }
  else {
      old = elem.childNodes.length
      return new Promise((resolve, reject) => {
     setTimeout(() => {
       resolve(waitForPastedData(elem, old));
     }, 2000);
   });
  }
}
async function send_text(text) {
    const dataTransfer = new DataTransfer();
    dataTransfer.setData('text', text);
    const event = new ClipboardEvent('paste', {
          clipboardData: dataTransfer,
          bubbles: true
        });
    let el = document.querySelector('#main .copyable-area [contenteditable="true"][role="textbox"]')
    el.focus()
// select old text and replace with new
    document.execCommand("selectall");
    el.dispatchEvent(event)
    return await waitForPastedData(el, 0)
}
await send_text('yourtext')