Edit in JSFiddle

function charCount(text){
  return text.replace(/[\.,!?; ]*/g, '').length;
}
function g(el){
return document.getElementById(el);
}

g('input').onkeyup=function(){
g('label').innerHTML=charCount(this.value);
}

<textarea id='input'></textarea>
<label id='label'>0</label>
textarea{
  width: 100%;
  display: block;
}
label{
  display: inline-block;
  background: #efefef;
  border-radius: 3px;
  padding: 4px 10px;
}