错误：找不到模块'mongoose'

我正在使用节点v8.0.0和npm 5.0.0 。我刚开始写一个package.json如下

 { "name":"foobar_app", "version":"0.0.1", "description":"", "main":"app.js", "scripts":{ "test":"echo \"Error: no test specified\" && exit 1", "start":"node app.js" }, "author":"dps", "license":"ISC", "dependencies":{ "bluebird":"^3.5.1", "body-parser":"^1.18.2", "express":"^4.16.2", "kafka-node":"^2.2.3", "mongoose":"^4.13.4" } } 

并运行npm install然后是npm start命令。但在terminal Error: Cannot find module 'mongoose'正在显示…任何方式我能够通过npm --save mongoose命令解决问题，但为什么后面的过程是不可能……..？？？？？？？ 我的app.js如下所示

 var mongoose = require('mongoose'); var Schema = mongoose.Schema; var express = require('express'); var bodyParser = require('body-parser'); var app = express(); var Todo = new Schema({ name: String, age: Number, nationality: String }); var todo_model = mongoose.model('todos',Todo); mongoose.connect('mongodb://localhost/express-todo'); app.use( bodyParser.json() ); // to support JSON-encoded bodies app.use(bodyParser.urlencoded({ // to support URL-encoded bodies extended: true })); app.get('/', function(req, res) { todo_model.find(function(err, result) { console.log(result) ; var todo_info = { "todo_list" : result }; console.log(todo_info.todo_list[0].name); res.json(todo_info);});}); app.listen(3000, function() { console.log("running on 3000"); });