maheshsabnis / cranenode

Node.js

JavaScript

• console.log()
• Data STructures
  • Array

  let arr = [];  

• No Data Types
  • string
    • '' OR ""
    • length,
    • toUpper(), toLower(), reverse(), indexOf(), lastIndexOf(), etc.
    • Interpolation

    let fname= "A"; 
    let mname = "B";
    let lname = "C";

    let fulleName = fname + ' ' + mname + ' ' + lname;
    /* Interpolation
       ''.concate()
    */
    let fullNameInt = `${fname} ${mname} ${lname}`;

- [] is Array
    - sort(), reverse(), reduce(), indexOf(),
    - push(), pop(), shift(), unshift()
    - filter(), forEach(), and map()
    - find()
- new Date() Object for DateTime
- Object
    - Everything is Object
    - assign()
        - Same as Deep Copy
    - create()
        - Like Clone()
    - Object Literal aka JSON Object

    let obj = { x:10, y:20 };

    - keys() method
        - to read all keys of object into an array

    let keys = Object.keys(obj);
    /* keys [x,y] */
    let values = Object.values(obj);
    /* values [10,20] */

    let arr = [10,20,30];
    arr.push(40);
    /* Spread (...) Operator */
    arr = [...arr,50,60];

Programming With Node.js

• Create a package.json
  • The 'npm' cli
  • Way to create package.json
    • npm init
      • Wizard for creating pcakage.json
    • npm init -y
      • create a package.json with defaults
    • The 'script' block for defining commands for Build, Run, and Test
    • The 'devDependencies' block
      • Contains standard Npde.js packages those are required during development
        • npm install --save-dev [PACKAGE-NAME]
    • The 'dependencies' block
      • Contains all packages those are required during execution / production of the application
        • npm install --save [PACKAGE-NAME]
        • npm install [PACKAGE-NAME]
    • Installing packages at global scope
      • If you need packages for multiple Nopde.js apps on same machine
        • npm install --global [PACKAGE-NAME]
  • Running Node Application
    • node [NAME].js
  • IF using ES 6+ Packages for Application, then in package.json add 'types': 'module' to run the application

    /* OLD Node.js Package Loader */
    let obj = require('PACKAGE-NAME'); /* Used by Standard JS aka Comman.js */
    /* ES 6+ JS Standards */

    import {Exported CLASSES/METHODS FROM PACKSGE} from 'PACKAGE-NAME'

Node.js Standard Package

• Package for Web Server Creation
• Package for Accessing FIle System
  • Streaming and Buffering
• PAckage for IO Path
• Crypto, Security, OS, etc.

Node.js Third-Party Packages

• Web Application Framework
  • Express with bodyparser
  • Feathers
  • Nest
  • ... and many more
• Security
  • JSON Web Token
  • OpenAuth
• Database
  • MongoDB and Mongoose
  • mssql
  • pgsql
  • mysql
  • sequelize (ORM)
• GraphQL
• cors
• bodyParse (Not Required)

Node.js Programming

1. The Web Server using HTTP Module

• The http module
  • Foundation of HTTP Request Processing For Node.js Apps
  • Allows to create Http Server and Start listing
  • Capacilities to Read Header, Body, Url, and Method
• Web Server http Readable Stream Methods

        /* close: the channel on which the request is received */
        on(event: 'close', listener: () => void): this;
        /* data: Start Reading Data default is butter */
        on(event: 'data', listener: (chunk: any) => void): this;
            /* drain: The Received data is complete and the Channel Butter is over */
        on(event: 'drain', listener: () => void): this;
        /* end: The Received data is complete and current request is over */
        on(event: 'end', listener: () => void): this;   
        /* error: Error While Processing data */
        on(event: 'error', listener: (err: Error) => void): this;

var searchresponse = [{
  "order": [{
    "items": [{
        "route": "foo",
        "display": "foo",
        "employeeId": "ABC"
      },
      {
        "route": "bar",
        "display": "bar",
        "employeeId": "DEF"
      },
      {
        "route": "baz",
        "display": "baz",
        "employeeId": "GHI"
      },
      {
        "route": "qux",
        "display": "qux",
        "employeeId": "JKL"
      }
    ]
  }],
  "more": false
}];
 
var data1 = ["ABC", "DEF"];
var items = searchresponse[0].order[0].items;
var i = items.length;
while (i--) {
  if (data1.indexOf(items[i].employeeId) != -1) {
    items.splice(i, 1);
  }
}
console.log(searchresponse[0].order[0].items);
 

Node.js File Access

• The 'fs' module
  • IO Operations
  • Synchronous Method
    • Read / Write
      • Blocking Operations
  • Asynchronous
    • Read / Write
      • No Blocking on Internal ThreadPool
  • Directories
  • Files
  • Buffers
    • Streams
    • Pipe()
• The 'fs' + 'http' module for creation of Web Server

import fs from "fs";
import path xfrom "path";
import { fileURLToPath } from "url";


// 1. Read the Server Path
let __fileName = fileURLToPath(import.meta.url);
console.log(`File Name = ${__fileName}`);
// 2. Combine this with the actual Resource Path
let dirPath = path.join(__fileName, "./../../filesNew");

/* To Read the File */
// 1. Read the Server Path
let __fileName = fileURLToPath(import.meta.url);
console.log(`File Name = ${__fileName}`);
// 2. Combine this with the actual Resource Path
let filePath = path.join(__fileName, "./../../files/a.txt");
console.log(`File Path = ${filePath}`);
let data = fs.readFileSync(filePath, { encoding: "utf8" });

Node.js Modules

• First look for the module from the Current path, if found load it and cache it

• If Module not found from the current path, then look for the module from the Standard Node.js Module Library from the loaded Runtime and if found then load and cache it, if not found here also then throw Module Not Found Exception

• Creating Custom Modules

  • Use 'export' to export the Module, in ES 6+
    • Can be a Constant
    • Can be a Function / Method
    • Can be a Class
  • Use 'import' to import the module

Relational Database Access (MS-SQL Server) in Node.js Apps

• The 'mssql' package npm install mssql express

Express

• Route HTTP Methods
  • get(P1,P2), post(P1,P2), put(P1,P2), delete(P1,P2), etc
  • P1,
    • Endpoint URL
  • P2,
    • The RequestHandler Callback
      • Request and Response
        • headers
        • body
      • Response
        • send()
        • status()
        • json()
        • sendFile()
  • IRouter Interface
    • Explicit Routing
  • use() method
    • USed to Register 'Middlewares' inside the HTTP Request Processing
      • cors()
      • json()
        • Older Days it was bodyParser (deprecated)
      • Static Files
        • JS, HTML, CSS
      • session
      • JWT
  • listen()
    • Expose the EndPoint
  • MAke sure that the Express is configured with Cross-Origin-Respource-Sharing (CORS) moiddleware so that the Requerst to API from Different Server is accepted
    • npm install cors
    • instance.use(cors())
      • The 'instance' is an express object