To manually test, press and hold down 'a' and select one of the accented characters.
You should observe that the replacement accented character does not replace 'a'.
Then insert an emoji using the emoji picker. This should insert something into the editor.
Finally, select all the content and attempt to replace it with an emoji. This should do nothing.
ac
(1) Typing 'a'...
(editable): type=beforeinput, inputType=insertText, data=a, dataTransfer=(null)
(editable): type=input, inputType=insertText, data=a, dataTransfer=(null)
The editor now has text content: a
(2) Preventing default when replacing 'a' with 'b'...
(editable): type=beforeinput, inputType=insertReplacementText, data=null, dataTransfer=plain:"b", html:"b"
The editor now has text content: a
(3) Inserting 'c' after 'a'...
(editable): type=beforeinput, inputType=insertText, data=c, dataTransfer=(null)
(editable): type=input, inputType=insertText, data=c, dataTransfer=(null)
The editor now has text content: ac
(4) Selecting all and preventing replacement with 'd'...
(editable): type=beforeinput, inputType=insertReplacementText, data=null, dataTransfer=plain:"d", html:"d"
The editor now has text content: ac