JSFiddle - React, Tailwind, and code Playground

HTML

<select id="myBox">
  <option >Volvo</option>
  <option>02</option>
  <option >Mercedes</option>
  <option >04</option>
</select>

JavaScript

var myExpectedResult = null ;
    
    $('#myBox').change(function(){ console.log('changed');
     // parse the value to a decimal based integer
     // @see http://www.w3schools.com/jsref/jsref_parseInt.asp
      var value = parseInt($(this).val(),10);
    
      myExpectedResult = value + 10; //other value must be decimal number too
    
      console.log('this is my expected result = '+myExpectedResult );
    });