javascript - mongodb使用mongoose没有办法链接，但是软件Robomongo和命令mongo都可以连接-PHP中文网问答

问题如题。写了个小程序，突然之间就没有办法连上了，之前还可以的。
mongodb 和程序都是在本地mongodb 是用brew 安装的。网上查了好多，还是没找到原因，数据库的文件夹也重新删除过，还是不管用。求老司机指导，贴一下代码吧。

let mongoose = require("mongoose");
let utils = require("./utils");
var log4js = require('log4js');
//log the  logger messages to a file, and the console ones as well.
log4js.configure({
    appenders: [
        {
            type: "file",
            filename: "log/trace_all.log",
        },
        {
            type: "console"
        }
    ],
    replaceConsole: true
});
//regist model 
require("./models/comment");
let CommentModel = mongoose.model("Comment");

mongoose.connect("mongodb://localhost:27017/acfun");
let db = mongoose.connection;
db.once("open", () => {
    console.log("mongoose connect mongodb://localhost:27017/acfun success");
});
db.on("error", (err) => {
    console.log(`db error : ${err}`);
    setTimeout(()=>{
        mongoose.connect("mongodb://localhost:27017/acfun");
    },500);
});

let mongoose = require('mongoose') let conStr = 'mongodb://127.0.0.1/app' mongoose.Promise = global.Promise /*mongoose.set('debug', true)*/ const conn = mongoose.createConnection(conStr) mongoose.connection.on('error', console.error.bind(console, '数据库连接错误\n')) mongoose.connection.on('connected', console.log.bind(console, '成功连接到数据库\n\n\n')) module.exports = conn