JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" size="5" class="value" name="value1" />
   <input type="text" size="5" class="value" name="value2" />
   <input type="text" size="5" class="value" name="value3" />
   <input type="text" size="5" id="total" readonly="readonly" class="bckground" name="total" />

JavaScript

function test() {
    document.getElementById('somevar').value = '25';
alert(document.getElementById('somevar').value );
}