JSFiddle - React, Tailwind, and code Playground

HTML

<select class='sel1'>
    <option>a</option>
    <option>b</option>
    <option>c</option>
</select><select class='sel2'>
    <option>test one</option>
    <option>test two</option>
    <option>test three</option>
</select>

JavaScript

$(document).ready(function() {
    // This code just makes it encoded
    $('select.sel2').find('option').each(function() {
        $(this).html(encodeURIComponent($(this).html()));
    });
    
    // This is what you want
    $('select.sel2').change(function() {
        var $this = $(this);
        $this.find('option:selected').html(decodeURIComponent($this.find('option:selected').html())).appendTo('select.sel1'); // append selected option to sibling
    });   
});