JSFiddle - React, Tailwind, and code Playground

HTML

<input type="number" name="numero1" id="number1">
<input type="number" name="numero2" id="number2">

<button>media</button>

JavaScript

var numero1 = document.querySelector("#number1");
var numero2 = document.querySelector("#number2");

var botao = document.querySelector("button");

botao.onclick = () => {
  var n1 = Number(numero1.value);  
  var n2 = Number(numero2.value);
  
	var media = (n1 + n2) / 2;

  alert("MĂ©dia: " + media);
}