如图：设定到期时间，到时间让topping字段为空或者删除，取消置顶的功能，在定时项目中，报错：排序字符不合法。求大神指教：

插入timelength字段代码：

async confirm(e) {
        const that = this;
        const code = that.data.code;
        const timelength = new Date() + code*1000*60*60;
        const index = that.data.index;
        const wehicle = that.data.wehicles[index];
        const wehicles = that.data.wehicles;
        wx.showLoading({
            title: "正在置顶中..."
        })
            wx.cloud.callFunction({
                name: "topping",
                data: {
                    id: wehicle._id,
                    timelength: timelength,
                },
                success: res => {
                    console.log(res);
                    if(!wehicle.topping){
                        wehicle.topping = (timelength)
                    }else{
                        wehicle.topping.push(timelength)
                    }
                    wehicle.istoppinged = true;
                    wehicles[index] = wehicle;
                    if (wehicle.topping) {
                        wx.hideLoading();
                        wx.showToast({
                            title: "恭喜！置顶成功！",
                        })
                        setTimeout(function () {
                            that.setData({
                                show_input: false,
                                wehicles:wehicles
                            })
                        }, 800)
                    } else {
                        wx.showToast({
                        title: "置顶失败，请重新置顶！",
                        })
                    }
                }
            })
    },

定时器代码timer：

{
    "permissions": {
        "openapi": [
        ]
    },
     "triggers":[
        {
            "name":"mytimer",
            "type":"timer",
            "config":"*/10 * * * * * *"
        }
    ]
   
}

需要执行代码：

// 云函数入口文件
const cloud = require('wx-server-sdk')
cloud.init()
const db = cloud.database()
const _ = db.command
// 云函数入口函数
exports.main = async (event, context) => {
    const currentTime = new Date().getTime() // 当前时间的时间戳（毫秒）
    // 查询所有到期（即当前时间已超过timelength）的文档并更新他们，删除topping字段
    return await db.collection("wehicle").orderBy('topping.timelength','lt').watchChanges({
        onChange:snapshot => {
            snapshot.docs.forEach(doc => {
                if(doc.topping.timelength < currentTime){//如果当前时间超过了timelength，则更新文档，删除topping字段
                    db.collection("wehicle").doc(doc._id).update({data:{topping:[]}})//清空topping字段或设置为空数组（根据你的需求决定）
                }
            })
        }
    })
}