YelpCamp-like APP

Full stack app where users can login, post and review campgrounds, and comment.

NPM and NodeJS

node.js

node.js 是一个 JavaScript 运行时，它让 JavaScript 脱离了浏览器环境，可以直接在计算机上运行，如访问 PC 其他组件/在 server 端(其他的电脑上)运行，所以让 JS（或者说框架 Express) 可以作为后端语言，极大地拓展了 JavaScript 用途。

node.js 优点：有非阻塞，事件驱动 I/O 等特性，从而让高并发（high concurrency）在的轮询（Polling）和 comet 构建的应用中成为可能

npm

npm 是 NodeJS 的包管理器(NodeJS package manager)，一般是随同 NodeJS 一起安装，能解决 NodeJS 代码部署上的很多问题：

• 在 Node.js 上开发时，会用到很多别人已经写好的 javascript 代码，如果每当我们需要别人的代码时，都根据名字搜索一下，下载源码，解压，再使用，会非常麻烦——于是就出现了包管理器 npm。大家把自己写好的源码上传到 npm 官网上，如果要用某个或某些个，直接通过 npm 安装就可以了

注意： 如果您想更新到 XXX modules 的最新主版本（例如从 5.x.x 更新到 6.x.x），则需要手动更新 package.json 文件中的版本范围，然后再运行 npm update 命令，才能生效。

Route: 不只是指 path 变量

route 路由，在 web 开发中，“route”是指根据 url， 分配到对应的处理程序。 就是一个路径的解析，根据客户端提交的路径，将请求解析到相应的控制器上。 a mechanism where HTTP requests are routed to the code that handles them. To put simply, in the Router you determine what should happen when a user visits a certain page.

Used npm packages:

Express, mongoose, ejs

Demo

app's link

Web Dev Essence

Core Point 1 : RESTful routes

Conventional 7 routes

Alternative

routes(路由)——对应 web 开发中间一环，"处理"

Routes are the program(code) that are responsible for listening and receiving requests and then deciding what to send back.

路由：url 对应分配到的处理程序

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Restful

REST, Representational State Transfer 是一种网络架构的风格，具有这种风格的系统可以称为是 RESTful 的。 或者更直白地說：Restful is just a pattern for defining routes, by mapping HTTP requests(C 端发起的请求) to CRUD operations(S 端处理请求的方式).

Why Restful? Benefits?

直观地从 URL 、发送的http 请求(GET、POST、DELETE...)、以及请求所得到的状态码，就知道做了什么操作，结果如何

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What is "CRUD"?

4 basic types of (DB) actions: Create, Read, Update, and Delete. 增删改查

(上文的 7 routes 实则是 CRUD： Read 对应 2 个 + C U D 3 个 + Create 和 Update 需先用 Read 2 个, 但得根据实际的业务需求来定义 routes，所以routes 的组合并不唯一)

和 DB 交互的实现：Mongoose module， 在程序内负责：连接接 DB+处理 CRUD

mongoose: an Object Data Modeling (ODM) Library for MongoDB and Node.js, provides a straight-forward, schema-based solution to MODEL application data.

是针对 MongoDB 操作的一个对象模型库

1. 和 mongoDB建立连接
2. 封装了 MongoDB 对文档的的一些增删改查等常用方法

让NodeJS 操作 Mongodb 数据库变得更加灵活简单

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Advanced: Nested Routes

we take the campground in the ID and just put it before all of the routes that have to do with comments.

Why? Dependency Because a comment is dependent on a campground. They are inherently linked. Inside the CREATE, we're not just going to make a comment: make a comment + then associate it with the campground.

So we're going to have to do a find by ID for camp ground.

How this helps?

By following this pattern, you don’t have to reinvent the wheel every time you build a new CRUD app. The routes and method names have already been decided so that you can run the action by directly editing URL !!!

Core Point 2: Data Associations

Introduction to Associations: 3 types

• one to one
• one to many
• many to many

2 ways of writing associations

focus on one to many here exmaple: user - entire posts

way1: Embedding Entire Data in JS array [] (No referencinng ID!) -> Embedded data is not a doc in DB

very straightfoward

way2: References Data(Object References)

1. build reference in schema first

2. refrence the post by normal .push as well

3. show only IDs vs show complete data

• in .save() method's callback after pushing, its return value "user" shows only post IDs

• use findOne(userName: userName).populate("post").excute(func(err, user)) to show complete data in referenced posts

Core Point 3: Authentication