Exec command insertText isn't working as expected on facebook.com

Question

This is a contenteditable element that you can create posts on facebook.com

All I want is inserting text into that contenteditable while keeping the new lines.

document.execCommand("insertText", false,"a sentence with \n\r a new line")

is not working, it just stripes \n and \r as we saw in the screenshot:

I have tried insertHTML, insertParagraph commands but no luck.

I have seen that they append a <br/> element when I press "Enter", so I also tried to append a <br/> element but it doesn't work

Changing .value, .textContent, innerHTML, innerText is not working as well.

I can't provide a MRE as it's a protected route.

Answer 1

Insert it in lines and manually dispatch the ShiftEnter key in-between:

function insertText(text, elem = document.querySelector('[contenteditable=true]')) {
  elem.focus();
  for (let i = 0, lines = text.split(/\r?\n/); i < lines.length; i++) {
    // send a dummy keyCode:0 first to initialize the editor's React state.
    elem.dispatchEvent(new KeyboardEvent('keydown', {keyCode: i && 13, shiftKey: true}));
    document.execCommand('insertText', false, lines[i]);
  }
}

Then call it as insertText('foo\nbar')