JSFiddle - React, Tailwind, and code Playground

HTML

<input id="myInput" oninput="checkInput()">
<button id="myButton">Button</button>

JavaScript

function checkInput() {
  const btn = document.querySelector('#myButton');
  const input = document.querySelector('#myInput');
  
  btn.disabled = input.value.trim().length === 0;
}

checkInput();