<form method="post">
    roomName : <input type="text" name="roomName" value="<%=room.roomName%>"/><br/>
    roomContent:<textarea name="roomContent"><%=room.roomContent%></textarea><br/>
    roomCreateUser:<input type="text" value="<%=room.roomCreateUser%>" name="roomCreateUser"/><br/>
    roomChat:<input type="radio" name="roomChat" value="public" checked>公聊<input type="radio" name="roomChat" value="secret" >私聊<br/>
    <input type="hidden" name="id" value="<%=room._id%>"/>

    <input type="submit" value="submit"/>
    <input type="reset" value="reset"/>
</form>
<script>
    function chatradio(cName,cValue){
        var cObj = document.getElementsByName(cName);

        for(var i = 0;i < cObj.length;i++){
            if(cObj[i].value == cValue){
                cObj[i].checked =  'checked';
            }
        }
    };
    chatradio('roomchat','<%=room.roomChat%>');
</script>

我想将后台已经有的roomChat值给html页面上对应的值checked一下，再显示到html页面的对应选项上，在网上找到了上述的方法自己改了一下变成了上面的代码，但是哪里还出了问题，导致仍然不能正确checked后台的值？