JSFiddle - React, Tailwind, and code Playground

by David Joseph Guzsik

HTML

<select id="dropdown">
  <option value="null">none</option>
  <option>1</option>
  <option>2</option>
  <option>3</option>
  <option>4</option>
  <option>5</option>
</select>

<button id="check">Check value</button>

JavaScript

var dd = document.getElementById('dropdown');

dd.addEventListener('change', function(){
  var value = this.value;
  if (value === 'null')
    sessionStorage.removeItem('key');
  else sessionStorage.setItem('key', value);
});

var check = document.getElementById('check');
check.addEventListener('click', function(){
    this.innerHTML = 'Value: '+sessionStorage.getItem('key')+
                     ', check: '+(!sessionStorage.getItem('key'));
});