пример (https://ru.stackoverflow.com/questions/806800/%D0%9A%D0%B0%D0%BA-%D0%BF%D0%BE%D1%81%D1%82%D0%B0%D0%B2%D0%B8%D1%82%D1%8C-%D0%BA%D1%83%D1%80%D1%81%D0%BE%D1%80-%D0%B2-%D0%BA%D0%BE%D0%BD%D0%B5%D1%86-contenteditable)
<div contenteditable="true">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repudiandae quo ratione assumenda quam deserunt, a corporis vero ipsum vitae, id libero veniam error ipsa. Magnam molestiae sapiente delectus modi odio.</div>
<button>Click me!</button>
const div = document.querySelector('div');
document.querySelector('button').addEventListener('click', () => {
const range = document.createRange();
range.selectNodeContents(div);
range.collapse(false);
const sel = window.getSelection();
sel.removeAllRanges();
sel.addRange(range);
});
const div = $('div').get(0); // или $('div')[0];
$('button').on('click', () => {
const range = document.createRange();
range.selectNodeContents(div);
range.collapse(false);
const sel = window.getSelection();
sel.removeAllRanges();
sel.addRange(range);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div contenteditable="true">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repudiandae quo ratione assumenda quam deserunt, a corporis vero ipsum vitae, id libero veniam error ipsa. Magnam molestiae sapiente delectus modi odio.</div>
<button>Click me!</button>