To paste as plain text with JavaScript execCommand, we get the pasted data as plain text before we insert it.
For instance, we write
editor.addEventListener("paste", (e) => {
e.preventDefault();
const text = e.clipboardData.getData("text/plain");
document.execCommand("insertHTML", false, text);
});
to listen to the past event on editor with addEventListener.
In it, we call preventDefault to stop the default paste behavior.
Then we get the pasted text as plain text by calling clipboardData.getData with 'text/plain',
Finally, we call execCommand to insert the text into editor.
