$('#articleTitle').bind('input propertychange',function () {

            var a = $(this).val().length;

            if(a>30){

                var val = $(this).val().substr(0,30);

                $(this).val(val);

                $('#helpBlock2').html(30);

            }else{

                $('#helpBlock2').html(a);

            }

        });

<div class="row" >

                                                <!--第三排 13-->

                                                <div class="col-md-1 text-right">

                                                    标题：

                                                </div>

                                                <div class="col-md-6 list-inline">

                                                    <input class="form-control input-sm" id="articleTitle" type="text" name="title" value="" placeholder="新闻标题,最大30字"  />

                                                </div>

                                                <div style="margin-top:5px;font-size: 14px;">

                                                    <span id="helpBlock2" style="color: red;">0</span><span>/30字</span>

                                                </div>

                                            </div>