<noscript>
        <div  style="color:red">您的浏览器不支持javascript,部分功能无法使用</div>
      </noscript>
  <div id="js_support" style="display:none">
      <p id="pSubmit"><input type="submit" name="registerform" value="注  册"  onclick="return submitform();"/></p>
      </div>
      <script type="text/javascript">
  $("js_support").style.display = "block";
</script>

      <noscript>
        <div  style="color:red">您的浏览器不支持javascript,部分功能无法使用</div>
      </noscript>

<div id="js_support" style="display:none">
      <p id="pSubmit"><input type="submit" name="registerform" value="注  册"  onclick="return submitform();"/></p>
      </div>
      
      <script type="text/javascript">
  $("js_support").style.display = "block";
</script>
      

<input  type="text"  class="textbox" onfocus="checkLogin(this);" onkeyup="checkLogin(this);" style="width:120px;" />

function checkLogin(node) {
    clearError();
    if (bp.String.trim(node.value)!="") {
      var url = "/test/response_validate";
      var params = [];
      params["command"] = "logincheck";
      params["login"] = encodeURI(bp.String.trim(node.value));
      var v = validatePath("login",params["login"]);
      if (v==""){
        bp.Io.XhrGet({
          url: url,
          mimeType: "text/json",
          params: params,
          load: function(type, data, e) {
            if (data==true){
              loginError = document.getElementById("valstatus").innerHTML = '登录名已存在';
              document.getElementById("loginValidate").className = "icon_cross";
              node.className = "input_error";
              loginValid = false;
            } else {
              loginError = "";
              document.getElementById("loginValidate").className = "icon_ok";
              node.className = "textbox";
              loginValid = true;
            }
          },
          error: function(type, data, e) {}
        });
      } else {
        loginError = document.getElementById("valstatus").innerHTML = v;
        document.getElementById("loginValidate").className = "icon_cross";
        node.className = "input_error";
        loginValid = false
      }
    } else {
      loginError = validatePath("login", "");
      document.getElementById("loginValidate").className = "";
      node.className = "textbox";
    }
  }

  def response_validate
       if params[:login]
      name = params[:login]
      puts name
      if name == "aaaaaa"
      @value = true
      render :partial => 'show_info'
      else
        @value = false
        render :partial => 'show_info'
      end  
    end
  end

<span id="valstatus"></span>
<td><input name="loginname" type="text" id="ctl00_main_content_txtLogin" class="textbox" onfocus="checkLogin(this);" onkeyup="checkLogin(this);" style="width:120px;" /></td>

  function createXmlHttpRequest(){ //创建对象
    try{
      xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
      try{
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
      }catch(e2){
        xmlHttp = false;
      }
    }
    if(!xmlHttp && typeof XMLHttpRequest != "undefined")
    {
      xmlHttp = new XMLHttpRequest();
    }  
  }
  
    function checkLogin(node){ // html中触发的js函数
    var loginname = document.getElementById('ctl00_main_content_txtLogin').value;
    createXmlHttpRequest();
    xmlHttp.open("Get","/home/response_validate?login="+loginname+"&ts="+new Date().toString(),true);
    xmlHttp.send(null);
    xmlHttp.onreadystatechange = processor; //注意这里processor不能有括号
  }
  
    function processor(){   //回调函数
    if(xmlHttp.readyState == 4  || xmlHttp.readyState == 'complete'){ //注意S要大写
      if (xmlHttp.status == 200){
        var    responsetext = xmlHttp.responseText;      
        if((responsetext.toString()) == "true"){
          loginError = document.getElementById("valstatus").innerHTML = '该登录名已经被使用';   
          
        }else{
         alert("测试");
        }
      }
    }
  }

  def response_validate
    @login_name = params[:login]    
    @value = true
   render :partial=>'response_validate'
  end

<%= @value %>