将光标设置在可满足div的子字符串末尾

Question

用户在此处输入一些字符串，并且该字符串包含Mahi为子字符串。我试图将光标Mahi放在单击按钮的末尾吗？

.html

<div id="demo" contenteditable="true"></div>

<button id="btn" onclick="focusAtMen()"></button>

js

// lets suppose user input is "Hi.......Mahi, .....?";

// here dots may be any characters

focusAtMen(){

var editor = document.getElementById("demo");

// set focus on `contentEditable div` and `place cursor at the end` of `Mahi` , thats a user Input.

}