JSFiddle - React, Tailwind, and code Playground

HTML

<select class="text_select" id="field_6" name="field_6">    
<option value="- Select -">- Select -</option>  
<option value="Option One">Option One</option>  
<option value="Option Two">Option Two</option>  
<option value="Option Three">Option Three</option>  
</select>

<label class="form_field">Your selected <span id="aggregator_name"></span>?</label>

JavaScript

function notEmpty(){

var e = document.getElementById("field_6");
var strUser = e.options[e.selectedIndex].value;
document.getElementById('aggregator_name').innerHTML = strUser;

}
notEmpty()
    
    document.getElementById("field_6").onchange = notEmpty;