textarea显示全部内容支持高度自适应

function readyNumber() { 

  $('textarea').each(function () {
     this.setAttribute('style', 'height:' + (this.scrollHeight) + 'px;overflow-y:hidden;');
  }).on('input', function () {
  this.style.height = 'auto';
  this.style.height = (this.scrollHeight) + 'px';
  })

}

readyNumber()