整理一个入门级的CURD操作：

let mongoose=require('mongoose');

let Customer=mongoose.model("Customer",{cname:String,salary:Number,birth:Date});

mongoose.connect("mongodb://localhost:27017/demo01")
.then(con=>{

    /*复位并添加一系列的试验数据*/
    // resetDb(function () {
    //     addMany(function () {
    //         con.disconnect();
    //     })
    // });

    /*添加一个*/
    // addCustomer(newObj=>con.disconnect())

    /*删除一个*/
    // deleteCustomer(rs=>{con.disconnect();console.log(rs)})

    /*更新数据*/
    update(newObj=>{con.disconnect();console.log(newObj)})
});

/* 数据清空 */
function resetDb(callback) {
    Customer.deleteMany({}).then(()=>callback())
}
/* 添加一行数据 */
function addCustomer(callback) {
    let c1=new Customer({cname:'tom',salary: 300.00,birth: new Date()});

    c1.save().then(newObj=>callback(newObj));
}

/* 添加试验数据 */
function addMany(callback) {
    let cs=[
        {cname:'tom',salary: 300.00,birth: new Date(1988,9,21)},
        {cname:'jackson',salary: 700.00,birth: new Date(1970,3,15)},
        {cname:'alice',salary: 400.00,birth: new Date(1999,7,10)},
        {cname:'john',salary: 900.00,birth: new Date(1977,1,5)},
        {cname:'linus',salary: 1200.00,birth: new Date(1965,6,21)}
        ]

   Customer.insertMany(cs,{ordered:true})
       .then(newObjs=>callback(newObjs))
}

function deleteCustomer(callback) {
    //成功的返回：{ n: 1, ok: 1, deletedCount: 1 }
    Customer.deleteOne({_id:'5c8f528f80964d4d5382fcb3'})
        .then(rs=>callback(rs))

}


function update(callback) {
    Customer.findOneAndUpdate({_id:'5c8f4c2c29c37c4ced64929f'},{$inc:{salary:100}},{new:true})
        .then(newObj=>callback(newObj))
}