JSFiddle - React, Tailwind, and code Playground

HTML

<p>Calculate sum of two numbers !</p>
    Enter 1rst Number:<br>
    <input type="number" class="first" placeholder=""><br><br>
    Enter 2nd Number:<br>
    <input type="number" class="second" placeholder=""><br><br>
    <input type="button" onclick="calculate()" value="calculate">
    <p class="result"></p>

JavaScript

function calculate() {
  var numberOne = document.querySelector(".first").value;
  var numberTwo = document.querySelector(".second").value;
  var sum = parseInt(numberOne) + parseInt(numberTwo);

  document.querySelector(".result").innerHTML = "The sum of the two numbers is : " + sum;
}