<div class="textar" oninput="chDIV()"style="white-space :pre; background:#999"contenteditable="true"></div>
<p style="white-space :pre; background:#000; color:#fff"></p>
<script>
  function chDIV(){
    var textar = document.querySelector('.textar');
    var p = document.querySelectorAll('p');
    
    var cleaned = textar.innerHTML.replace(/"<div>/g,"\n").replace(/<\/div>/g,"").replace(/<br>/g,"");
    var matches = cleaned.split('\\n').join('').match(/\n/gi);
    
    if (matches === null) {
      return;
    }
    
    p[0].innerText = matches.length
  }
</script>

func