<input type="text" value="我是输入的文字" maxlength="10" id="detail1"/>
<p><span id="detail1_num">0</span>/<span>10</span></p>
<textarea placeholder="最多输入100字" rows="3" maxlength="100" class="editDetail" id="detail2" >呵呵</textarea>
<p><span id="detail2_num">0</span>/<span>100</span></p>

$(function(){ 
 /*input字数*/
 /*在页面刚载入时先显示出输入框的字数*/
 var text1=$("#detail1").val();
 var counter1=text1.length;
 $("#detail1_num").text(counter1);
 /*添加触发事件进行动态计算输入框的字数*/
 $("#detail1").on('blur keyup input',function(){
 var text=$("#detail1").val();
 var counter=text.length;
 $("#detail1_num").text(counter);
 });
 /* textarea字数*/
 var text2=$("#detail2").val();
 var counter2=text2.length;
 $("#detail2_num").text(counter2);
 $("#detail2").on('blur keyup input',function(){
 var text=$("#detail2").val();
 var counter=text.length;
 $("#detail2_num").text(counter);
 });
});