js里面获取session值，判断登录与否

 //判断登录与否
    $(".is_login").click(function () {
        var account_id = "{$Think.session.user_info.id}";
        if (account_id=="") {
            layer.confirm('您需要登录后才能发表话题，是否前往登录？', {
                btn: ['确定', '取消'], //按钮
                cancel: function(index){
                    layer.close(index);
                },title:'发表提示',
            }, function () {
                window.location.href = "{:url('index/login/index')}";
            }, function (index) {
                layer.close(index);
            });
        }
    });