JSFiddle - React, Tailwind, and code Playground

HTML

<label for="method">How?</label>
    <select id="method" name="method" required>
      <option name="method"  value="email">Email</option>
      <option name="method" value="web">Web</option>
    </select>
    <span class="help-text">The web, or email?</span>
  </label>

  <label id="contact-label" for="contact">Email Address</label>
  <input type="email" name="contact" id="contact" value="" maxlength="255">
  <span class="help-text">e.g. stuff@yourdomain.com</span>

JavaScript

$(document).ready(
  function() {
    $('#method').change(
      function(){
        var method = $('option:selected',this).text();
          if method == "Email" {
              $('#contact-label').text("Email Address"); 
          } else if method == "Web" {
              $('#contact-label').text("App URL"); 
          }
      }
      );
  }
  );