count: (获取记录的条数)

<button type="primary" bindtap="btnNum">查询个数</button>

btnNum() {
        db.collection("demoUser").count()
        .then(res => {
            console.log(res);
        })
    },

watch监听事件

    getData() {
        db.collection("demoUser")
        .get()
        .then(res => {
            this.setData({
                dataArr:res.data
            })
        })
    },
    /**
     * 生命周期函数--监听页面加载
     */
    onLoad: function (options) {
        this.getData();

        db.collection("demoUser").watch({
            onChange:res => {
                console.log(res)
            },
            onError:err => {
                console.log(err)
            }
        })
    },

<view wx:for="{{dataArr}}" wx:key="index">{{index + 1}}.{{item.title}}</view>

删除后立即显示,点赞功能，接受任务功能
    onLoad: function (options) {
        this.getData();

        db.collection("demoUser").watch({
            onChange:res => {
                this.setData({
                    dataArr:res.docs // *
                })
            },
            onError:err => {
                console.log(err)
            }
        })
    },