1. const vs var vs let

const : block scope, constant value in block let : block scope var : function scope

2. Arrow functions

let arrFunc1 = (arg1, arg2, arg3) => {

}

// OR
let arrFunc2 = arg1 => console.log('Some one line code instead of console.log');

// OR
let arrFunc2 = (arg1, arg2) => console.log('Some one line code instead of console.log');

3. Promises

let somePromise = new Promise((resolve, reject) => {

  // if successful execution
  resolve(result);

  // else
  reject(err);

});

somePromise
.then((result) => {
  // todo next step after getting result
})
.catch((error) => {
  // handle error
});
;

And remember about this

4. require()

const http      = require('http'); // default Node module/ module inside node_modules folder
const myModule1 = require('path/to/file/relative/dir/myModule1.js'); 
const myModule2 = require('path/to/file/relative/dir/myModule2'); //No need to mention .js extension
const myModule3 = require('path/to/file/relative/dir/'); //No need to mention index.js for including index.js

1. Request is received by the server by the server.serve method (http.createServer())
2. _getRequestParams obtains the whole request object in the required format
3. We choose a handler from our existing set of handlers as per the url and method
4. We call the handler and let it handle the request
5. Handler makes additional DB/API requests if needed
6. Once the handler handles the request, it callbacks with an appropriate response object and status
7. _generateResponse() just writes the result object and status to HTTP response

1. _getRequestParams recieves payload in pieces, so that takes place over a period asynchronously. Thus _getRequestParams returns a Promise
2. the handler may make DB/API requests that happen in the background asynchronously. Thus every handler returns a Promise of handling the request

There are lot of HTTP methods a) GET : get data/resource b) POST: create new data/resource c) PUT : update existing data/resource d) DELETE: delete existing data/resource e) PATCH: partial update of data

  www.example.com/urlpath/for/some/task
  urlpath: /urlpath/for/some/task

syntax wise it looks like linux's path syntax

  www.example.com/urlpath/for/some/task?param1=val1&param2=val2
  queryParams: {param1: val1, param2 : val2}

Additional parameters you can add to the overall url, used a lot in GET. Multiple params are separated by a '&' Sometimes the | is also used to pass a list of values like for

param1 : [val1,val2,val3]
?param1=val1|val2|val3

However I found this syntax isn't widely used

1. Provide key-value pair information
2. Usually used for userTokens and authentication
3. Payload type like application/json can also be mentioned
4. Many websites use specific Cache Headers to instruct browser how to cache the site

Possible payloads

1. Form data (key-value based)
2. File uploads (raw data)
3. Structured data like JSON, XML

projectDir/
  .git
  .gitignore

  index.js
  lib/
    config/
      index.js  // Main config setup
      cert.pem  // http
      key.pem
    handlers/
      index.js // Main handler
    server.js