html 检验复选框是否被勾选

• input checkbox 检验是否被勾选

            <div>
                 <font color = "red">*</font>3、您认为目前平台在网站建设中最需要改进的是哪些方面
                 </br></br>
                 <label><input type = "checkbox" value = "1" name = "test">&nbsp;页面设置</label>&nbsp;&nbsp;</br></br>
                 <label><input type = "checkbox" value = "2" name = "test">&nbsp;网站功能</label>&nbsp;&nbsp;</br></br>
                 <label><input type = "checkbox" value = "3" name = "test">&nbsp;网站管理</label>&nbsp;&nbsp;</br></br>
                 <label><input type = "checkbox" value = "4" name = "test">&nbsp;网站服务</label>&nbsp;&nbsp;</br></br>
             </div>

  <script type="text/javascript">
  function conInfo(){
        var strArr = 'five3';
            var flag = false;
            for(var i=0;i<document.getElementsByName(strArr).length;i++){ 
                if(document.getElementsByName(strArr[i].checked==true){
                    flag = true;
                }
            } 
            if(!flag){
                    alert("红色‘*’号标识题目为必填题目"+",请填写完整后再提交");//弹出选中单选按钮的值
                    return false;
            }
    }
  </script>