JSFiddle - React, Tailwind, and code Playground

HTML

<select id="select1">

<option value="1">this</option>
<option value="2">that</option>
<option value="3">other</option>

</select>

<input type="button" id="but" value="get all values">
<select id="select2" multiple="true">

<option value="1" >this</option>
<option value="2">that</option>
<option value="3">other</option>

</select>

JavaScript

$('#select1').append('<option value="4">another</option>');

$('#but').click(function(){
    $('#select2 :selected').each(function(){
        alert($(this).text() + " : " + $(this).val()); 
    });
});