JSFiddle - React, Tailwind, and code Playground

HTML

<select name="from_currency" id="from_currency">
                  <option value="USD">USD : United States Dollar</option> 
                  <option value="EUR">EUR : Euro</option> 
                  <option value="JPY">JPY : Japanese Yen</option>
                  <option value="INR">INR : Indian Rupee</option>
     </select>
<br/>

    <select name="to_currency" id="to_currency"> 
                  <option value="EUR">EUR : Euro</option>  
                  <option value="USD">USD : United States Dollar</option> 
                  <option value="JPY">JPY : Japanese Yen</option>
                  <option value="INR">INR : Indian Rupee</option>
     </select>

<br/>

<input type="button" id="switchid" value="Switch"/>

JavaScript

$("body").on("click", "#switchid", function(){ 
      var frm = '';
      var to ='';
      frm = $("#from_currency").val(); 
      to = $("#to_currency option:selected").val(); 
      $("#to_currency").val(frm);
      $("#from_currency").val(to);
    });