<table style="width:320px;margin:40px auto;"> 
 <tr> 
  <th>密码</th> 
  <td><span class="tbl-txt"><input id="pass" class="input-style" size="30" maxlength="30" name="pass" type="text" /></span></td> 
 </tr> 
 <tr>  
  <th></th>   
  <td id="level" class="pw-strength">    
   <div class="pw-bar"></div> 
   <div class="pw-bar-on"></div> 
   <div class="pw-txt"> 
   <span>弱</span> 
   <span>中</span> 
   <span>强</span> 
   </div> 
  </td>  
 </tr> 
</table> 

.tbl-txt{font-size:14px;} 
  .tbl-txt input{padding:0 5px; height:22px; line-height:22px; margin-bottom:6px;} 
  .pw-strength {clear: both;position: relative;top: 8px;width: 180px;} 
  .pw-bar{background: url(images/pwd-1.png) no-repeat; position:relative; top:1px;height: 14px;overflow: hidden;width: 179px;} 
  .pw-bar-on{background: url(images/pwd-2.png) no-repeat; width:0px; height:14px;position: absolute;top: 1px;left: 2px;transition: width .5s ease-in;-moz-transition: width .5s ease-in;-webkit-transition: width .5s ease-in;-o-transition: width .5s ease-in;} 
  .pw-weak .pw-defule{ width:0px;} 
  .pw-weak .pw-bar-on {width: 60px;} 
  .pw-medium .pw-bar-on {width: 120px;} 
  .pw-strong .pw-bar-on {width: 179px;} 
  .pw-txt {padding-top: 2px;width: 180px;overflow: hidden;} 
  .pw-txt span {color: #707070;float: left;font-size: 12px;text-align: center;width: 58px;} 

$(function(){ 
 $('#pass').keyup(function () { 
  var strongRegex = new RegExp("^(?=.{8,})(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*\\W).*$", "g"); 
  var mediumRegex = new RegExp("^(?=.{7,})(((?=.*[A-Z])(?=.*[a-z]))|((?=.*[A-Z])(?=.*[0-9]))|((?=.*[a-z])(?=.*[0-9]))).*$", "g"); 
  var enoughRegex = new RegExp("(?=.{6,}).*", "g"); 
  
  if (false == enoughRegex.test($(this).val())) { 
   $('#level').removeClass('pw-weak'); 
   $('#level').removeClass('pw-medium'); 
   $('#level').removeClass('pw-strong'); 
   $('#level').addClass(' pw-defule'); 
    //密码小于六位的时候，密码强度图片都为灰色 
  } 
  else if (strongRegex.test($(this).val())) { 
   $('#level').removeClass('pw-weak'); 
   $('#level').removeClass('pw-medium'); 
   $('#level').removeClass('pw-strong'); 
   $('#level').addClass(' pw-strong'); 
    //密码为八位及以上并且字母数字特殊字符三项都包括,强度最强 
  } 
  else if (mediumRegex.test($(this).val())) { 
   $('#level').removeClass('pw-weak'); 
   $('#level').removeClass('pw-medium'); 
   $('#level').removeClass('pw-strong'); 
   $('#level').addClass(' pw-medium'); 
    //密码为七位及以上并且字母、数字、特殊字符三项中有两项，强度是中等 
  } 
  else { 
   $('#level').removeClass('pw-weak'); 
   $('#level').removeClass('pw-medium'); 
   $('#level').removeClass('pw-strong'); 
   $('#level').addClass('pw-weak'); 
    //如果密码为6为及以下，就算字母、数字、特殊字符三项都包括，强度也是弱的 
  } 
  return true; 
 }); 
})