jquery 实时判断textarea输入了多少个字，并通过parent,children显示字符数

html

```
        <form>
            <input class="form-control" id="title" placeholder="请输入标题"> 
            <div class="row rowdiv">
              <div class="col-10"><textarea class="form-control mt-1 shici_add_text" id="yuanwen" placeholder="请输入诗词原文"></textarea></div>
              <div class="col-2 ">0</div>
            </div>

<div class="row rowdiv">
              <div class="col-10"><textarea class="form-control mt-1 shici_add_text" id="shangxi" placeholder="请输入诗词赏析"></textarea></div>
              <div class="col-2"></div>
            </div>           
            
        </form>
```

js
```
  $('.rowdiv textarea').bind('input propertychange',function(){
    var count = $(this).val().length;
    if(count>16300){
      alert('字太多了');
    }
    $(this).parent().parent().children('.col-2').text(count)
  })
```