JSFiddle - React, Tailwind, and code Playground

HTML

<div>  
  <label>Password:</label>
  <input name="password" id="password" type="password" onkeyup='validatePassword();' />
</div>
<br/>
<div> 
  <label>Confirm password:</label>
  <input type="password" name="confirm_password" id="confirm_password"  onkeyup='validatePassword();' /> 
  <span id='message'></span>
</div>

JavaScript

function validatePassword() {
  if (document.getElementById('password').value ==
    document.getElementById('confirm_password').value) {
    document.getElementById('message').style.color = 'green';
    document.getElementById('message').innerHTML = 'matching';
  } else {
    document.getElementById('message').style.color = 'red';
    document.getElementById('message').innerHTML = 'not matching';
  }
}