兼容IE8 的清空input标签

这个问题还是有BUG 正在继续研究；我现在总结里几点清空缓存的方法

/* 清空页面的缓存信息 */
function clearLoginInput() {
document.getElementById("cellPhoneL").value = "";
document.getElementById("passWord").value = "";
document.getElementById("login_img_code").value = "";
document.getElementById("registerpassword").value = "";

if( !('placeholder' in document.createElement('input')) ){ 
  
    $('.ppl').each(function(){  
      var that = $(this),  
      text= that.attr('placeholder');  
      if(that.val()===""){  
        that.val(text).addClass('placeholder');  
      }  
      that.focus(function(){  
        if(that.val()===text){  
          that.val("").removeClass('placeholder');  
        }  
      })  
      .blur(function(){  
        if(that.val()===""){  
          that.val(text).addClass('placeholder');  
        }  
      })  
      .closest('form').submit(function(){  
        if(that.val() === text){  
          that.val('');  
        }  
      });
      if(that.val()==="密碼"){
      placeHolder(document.getElementById("passWord"),false);
      document.getElementById("passWord").attachEvent('onblur', loginPasswordVali);
      }
    });  
  }

}
<!--登陆star-->
<div class="login-zf" style="display: none;" id="loginSystem">
<span class="login-close1 login-closeBg" onclick="closeLogin()"></span>
<h3><fmt:message key="headtop.login"/></h3>
<div class="login-posit" id="login_div_cellPhoneL">
<input class="p-number ppl" type="text" placeholder="<fmt:message key="headtop.mobileuser"/>"
id="cellPhoneL" onblur="loginCellPhoneLValiIsBlank()" maxlength="50">
<p class="login-tip">
<span class="orange orange2" id="mobilecolde"></span> <i
class="login-close4 login-closeBg ml5" id="login_i_cellPhoneL"></i>
</p>
</div>
<div class="login-posit" id="login_div_passWord">
<input class="p-number ppl" type="password" placeholder="<fmt:message key="headtop.password"/>"
id="passWord" onblur="loginPasswordVali()" maxlength="16">
<p class="login-tip">
<span class="orange orange2" id="tishi"></span> <i class="login-close5 login-closeBg ml5"
id="login_i_passWord"></i>
</p>
</div>
<div class="login-positHou  clearfix">      
        <input class="m-number fl ppl" type="text" placeholder="<fmt:message key="headtop.validatecode"/>" id="login_img_code" maxlength="4" onblur="loginImgCodeVali()">
        <p class="login-tip2"><span class="orange orange2" id="login_span_imgCode"><!-- 验证码错误 --></span><i class="login-close4 login-closeBg ml5" id="login_i_imgCode"></i></p>
        <!-- <a href="" class="faisongBtn fr mt20"></a> -->
        <p class="faisongnian fr mt20"><img id="img_code" alt="<fmt:message key="headtop.validatenosee"/>" src="../verifyCode/getImage.do" onclick="getImage(this)"></p>
    </div>
<div class="login-jizhi">
<!-- <b class="login-close2 login-closeBg"></b> -->
<input type="checkbox"  id="remember"  class="fl"/><label class="fl" style="font-size: 12px;">&nbsp;<fmt:message key="headtop.rememberme"/></label>
<a href="javascript:void()" onclick="pwdForget()" class="fr blue"><fmt:message key="headtop.forgetpw"/></a>
<!--  -->
<div class="clearfix"></div>
</div>
<a href="javascript:void()" id="hx_dzb" class="loginBtn mt20" onclick="userLogin()"><fmt:message key="headtop.login"/></a>
<span id="tishi"></span>
<div class="mt20">
<span class="fl"><fmt:message key="headtop.nouser"/>？</span><a href="javascript:void()"
onclick="toRegister()" class="blue fl"><fmt:message key="headtop.quickregister"/></a>
</div>
</div>
<!-- 登录结束 -->

注意（必须下载一个：placeholder的插件）
==================================================================================
第二个方法！
document.getElementById("cellPhoneL").setAttribute("value","");
document.getElementById("passWord").setAttribute("value","");
document.getElementById("login_img_code").value = "";
document.getElementById("registerpassword").value = "";
if (!('placeholder' in document.createElement('input'))) {

$('input[placeholder],textarea[placeholder]').each(function() {
var that = $(this), text = that.attr('placeholder');
if (that.val() === "") {
that.val(text).addClass('placeholder');
}
that.focus(function() {
if (that.val() === text) {
that.val("").removeClass('placeholder');
}
}).blur(function() {
if (that.val() === "") {
that.val(text).addClass('placeholder');
}
}).closest('form').submit(function() {
if (that.val() === text) {
that.val('');
}
});
});
}

===============================================================================
第三个方法；
        $("#cellPhoneL").val("");
$("#cellPhoneL").attr("placeholder",$("#cellPhoneL").attr("placeholder"));
$("#passWord").val("");
$("#passWord").attr("placeholder",$("#passWord").attr("placeholder"));
$("#login_img_code").val("");
$("#login_img_code").attr("placeholder",$("#login_img_code").attr("placeholder"));
===============================================================================
第四个方法；