Edit in JSFiddle

var textareaLength = function () {
  $('.js-textarea').on('keydown keyup keypress change',function(){
    var length = $(this).val().length;
    $(this).next('.js-length').find('strong').html(length);
  });
}
textareaLength();



WebFontConfig = {
    google: { families: [ 'Dancing+Script:400,700:latin' ] }
  };
  (function() {
    var wf = document.createElement('script');
    wf.src = 'https://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js';
    wf.type = 'text/javascript';
    wf.async = 'true';
    var s = document.getElementsByTagName('script')[0];
    s.parentNode.insertBefore(wf, s);
  })();

<h1 class="h1">count text number</h1>

<div class="wrap">
  <div class="inner">
    <textarea class="textarea js-textarea" name="" id=""></textarea>
    <p class="length js-length"><strong></strong>／2000文字</p>
  </div>
</div>