David Kern davidkern13

JavaScript Bitwise Hacks

It assumes the highest positive signed 32-bit float value for numbers. In other words, 2147483647 (or 0x7FFFFFFF or 2^31-1).

Caching files Service Workers

@(js study notes)[js|dev|web]

##What is Cache API?

While this API was intended for service workers, it is actually exposed on the window so it can be accessed from anywhere in your script. The entry point is caches.

** Used to store assets that have a URL

MongoDB Cheat Sheet

Show All Databases

show dbs

Show Current Database

Node.js Deployment

Steps to deploy a Node.js app to DigitalOcean using PM2, NGINX as a reverse proxy and an SSL from LetsEncrypt

1. Sign up for Digital Ocean

If you use the referal link below, you get $10 free (1 or 2 months) https://m.do.co/c/5424d440c63a

2. Create a droplet and log in via ssh

I will be using the root user, but would suggest creating a new user

Interview Questions

Node.js

Q1: What do you mean by Asynchronous API? ☆☆

Answer: All APIs of Node.js library are aynchronous that is non-blocking. It essentially means a Node.js based server never waits for a API to return data. Server moves to next API after calling it and a notification mechanism of Events of Node.js helps server to get response from the previous API call.

Source: tutorialspoint.com

	var udp = require('dgram');

	// --------------------creating a udp server --------------------

	// creating a udp server
	var server = udp.createSocket('udp4');

	// emits when any error occurs
	server.on('error',function(error){
	console.log('Error: ' + error);

	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">

	<title>Chat</title>

	<script src="./socket.io/socket.io.js"></script>
	<script type="text/javascript">

	// The events are from https://www.w3.org/TR/html5/semantics-embedded-content.html#media-elements-event-summary
	import videojs from 'video.js'

	const Plugin = videojs.getPlugin('plugin')
	const EVENTS = [
	'loadstart',
	'progress',
	'suspend',
	'abort',
	'error',

	// EXAMINE THE DOCUMENT OBJECT //

	// console.dir(document);
	// console.log(document.domain);
	// console.log(document.URL);
	// console.log(document.title);
	// //document.title = 123;
	// console.log(document.doctype);
	// console.log(document.head);
	// console.log(document.body);

	const net = require('net');

	//
	// A Node.js port of this original Gist: https://gist.github.com/danielfaust/998441
	// To find hosts on the network: nmap -Pn -p55000 192.168.12.1/24
	//
	// Note: This is for Samsung TVs circa 2012-2015 that use a service running on port 55000
	// Samsung TV's circa 2016 and later use a WebSocket service on port 8001 which is different
	//