MERN Stack 2019

ES6, MongoDB Atlas and React Hooks

Node.JS (https://nodejs.org/en/)

NodeJS allows JavaScript to be written on the server as opposed to written in the browser. Synchronous -> Blocking IO Asynchronous -> Non-Blocking IO Node.JS is a single thread synchronous process. Therefore we must use callbacks in order to achieve an asynchronous non-blocking process (not technically asynchronous but feels that way). This can lead to 'Callback Hell', identified by the flying 'V' formation, if not written properly. We use Promises and/or Async/Await to avoid 'Callback Hell'.

NPM (https://www.npmjs.com/) Packages:

'npm Init' - to create package.json file.

'npm install' for regular dependencies (--save deprecated)

'npm i --save-dev or (-D)' for development dependencies

'npm i nodemon --global' (install globally, across your machine)

'npm uninstall nodemon' (deletes a package)

Common Packages:

"dependencies": {

"cors": "^2.8.5",
"dotenv": "^8.0.0",
"express": "^4.17.1",
"mongoose": "^5.6.2"

Requiring an NPM package in our app:

const express = require("express");

Express (https://expressjs.com/)

Basic Server:

const express = require("express");

const app = express();

app.get("/", (req, res) => {

res.status(200).json({ message: "Hello from the server!", app: "MERN Test" });

});

app.post("/", (req, res) => {

res.send(" post message test");

});

const port = process.env.PORT || 4000;

app.listen(port, () => {

console.log(App Running on port ${PORT} ...);

});

Express Middleware Stack

Order matters they are executed in the order they are entered. app.use(cors()); app.use(express.json())- (Body Parser) app.use("/users", usersRouter); app.use("/exercises", exercisesRouter);

MongoDB (https://cloud.mongodb.com)

There is very little to do with the MongoDB:

get connection string from MongoDB site and set in the dotenv file. MONGO_URI = 'connection string'
Import the .env file to the app.js file. const uri = process.env.MONGO_URI; Mongoose will take care of the rest of the MongoDB code.

Mongoose (https://mongoosejs.com)

Connection: get connection string from MongoDB site and set in the dotenv file.

const uri = process.env.MONGO_URI;

mongoose .connect(uri, { useNewUrlParser: true, useCreateIndex: true, useFindAndModify: false }) .then(() => console.log("Mongo Connected")) .catch(err => console.log(err));

Implementing CRUD functionality is a 3 step process

set models for each collection i.e. const mongoose = require("mongoose");

        const userSchema = new mongoose.Schema({
          username: {
            type: String,
            required: true,
            unique: true,
            trim: true,
            minlength: 3
          }
        });

        module.exports = mongoose.model("User", userSchema);

import models into routes and make routes
:

3) Require and use routes in the server.js i.e. const exercisesRouter = require("./routes/exercises"); const usersRouter = require("./routes/users");

    i.e. app.use("/users", usersRouter);
         app.use("/exercises", exercisesRouter);

         or combine into 1 line:
         app.use("/users", require("./routes/users"))

Github