JSFiddle - React, Tailwind, and code Playground

HTML

<select id='a' style='width:300px' size='5'>
    <option>a1</option>
    <option>a2</option>
    <option>a3</option>
    <option>a4</option>
    <option>a5</option>
    <option>a6</option>
</select><br/>
<input type='button' id='btn' value='Add'/>
<select id='b' style='width:300px' size='5'>
    <option>b1</option>
    <option>b2</option>
    <option>b3</option>
    <option>b4</option>
    <option>b5</option>
    <option>b6</option>
</select>

JavaScript

$(document).ready(function() {
    $('#btn').click(function() {
        //document.getElementById('a6').scrollIntoView();
        $('#a> option:selected').clone(false).appendTo('#b').get(0).scrollIntoView();
    });
});