第一步，安装mongoose模块
npm i mongoose -S
第二步，导入模块
const mongoose = require("mongoose");
第三步，连接数据库
mongoose.connect("mongodb://127.0.0.1/tyqaq");//（ps：tyqaq是库名）
其他步，添加些监听
获得获取数据库连接
const conn = mongoose.connection;
添加监听数据库连接事件
conn.on("connected",()=> {
console.log("数据库连接成功")
})
Events:（其他事件）
connecting: Emitted when connection.{open,openSet}() is executed on this connection.
connected: Emitted when this connection successfully connects to the db. May be emitted multiple times in reconnected scenarios.
open: Emitted after we connected and onOpen is executed on all of this connections models.
disconnecting: Emitted when connection.close() was executed.
disconnected: Emitted after getting disconnected from the db.
close: Emitted after we disconnected and onClose executed on all of this connections models.
reconnected: Emitted after we connected and subsequently disconnected, followed by successfully another successfull connection.
error: Emitted when an error occurs on this connection.
fullsetup: Emitted in a replica-set scenario, when primary and at least one seconaries specified in the connection string are connected.
all: Emitted in a replica-set scenario, when all nodes specified in the connection string are connected.
For practical reasons, a Connection equals a Db.
第四步，创建数据模型（集合，表）
exports.User = mongoose.model("users",{
account:String,
password:String,
photo:String,
createTime:Date,
ip:String
});
或者这样写
// name : { type:String },//属性name,类型为String
// age : { type:Number, default:0 },//属性age,类型为Number,默认为0
查找&&写入数据
router.post("/api/user/register", (req, res) => {
// 查找集合内account字段 有多少个 如果大于0表示账户存在，也就不写入
db.User.find({ account: req.body.account }).count(function (err, count) {
if (count > 0) {
res.json({ code: "fail", message: "帐户名存在！" })
} else {
//不大于0表示不存在 准备导入库
req.body.createTime = new Date();
req.body.ip = tools.formatIP(req.ip);
// 使用数据模型类创建一个用户对象，并且填充数据
var user = new db.User(req.body);
// 调用save方法将数据保存到数据库中
// 数据模型表示一类事物，它可以包含数据，还包含相应的数据操作方法
user.save(function (err, model, count) {
// console.log(arguments);
if (err) {
res.json({ code: "error", message: "服务端错误，请稍候在试！" })
} else {
res.json({ code: "success", message: "注册成功！" })
}
})
}
})
})
//创建一个筛选对象
var filter = {
account:req.body.account,
password:req.body.password
}
// 根据筛选条件查找。执行回调函数，
db.User.find(filter).exec(function (err,models) {
err存在数据库出错，不存在查看
models里包含内容