<div id="app">
  <label for="textarea">What is your favorite kind of taco?</label>
  <textarea id="textarea"></textarea>
  <br>
  <button class="button">Let us know!</button>
</div>
body {
  font-family: 'Bitter', serif;
}

#app {
  text-align: center;
  padding: 70px;
  max-width: 360px;
  font-size: 16px;
  margin: 0 auto;
  display: table;
  line-height: 2em;
}

label {
  padding-right: 10px;
  font-size: 18px;
  font-weight: bold;
}

button {
  border: none;
  color: white;
  padding: 0.5em 1em;
  border-radius: 3px;
  background: orangered;
}

textarea {
  margin-top: 10px;
}
$(function() {
  var button = $('.button');
  var textarea = $('#textarea');
  
  button.hide();
  textarea.keyup(function() {
    if (textarea.val().length > 0) {
      button.show();
    } else {
      button.hide();
    } 
  })
});
View Compiled

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js