jQuery keyup event fires only once
<p>Why does this jQuery event only fire once?</p>

<pre><code>$(document).on('keyup', '[data-behavior="oneliner-text-area"]', function (event) {
  var textLength = $(this).length;
  var textLengthLimit = 140;
  $('[data-behavior="oneliner-counter"]').html(textLengthLimit - textLength);
  if ((textLengthLimit - textLength) &lt; 0) {
    $('[data-behavior="oneliner-counter').addClass('oneliner-count-warning');
  }
});
</code></pre>