DEV Community: eddiejpot

Java Script Truthy/Falsy & Logical Operators

eddiejpot — Wed, 01 Dec 2021 04:22:57 +0000

Falsy Values

null
undefined
NaN
0
"" empty quotes
false

&& and ||

Returns the first falsy value
If none found, it will return the last truthy value

Returns the first truthy value
If none found, it will return the last falsy value

// both are truthy
truthy1 && truthy2; // truthy2
truthy1 || truthy2; // truthy1

// both are falsy
falsy1 && falsy2; // falsy1
falsy1 || falsy2; // falsy2

// 1st truthy, 2nd falsy
truthy1 && falsy1; // falsy1
truthy1 || falsy1; // truthy1

// 1st falsy, 2nd truthy
falsy1 && truthy1; // falsy1
falsy1 || truthy1; // truthy1

PostgreSQL: Drop a database that has a hyphen in the name

eddiejpot — Fri, 28 May 2021 01:24:10 +0000

Normally to drop a database in psql (postgresql) , we can just type

DROP DATABASE dbname;

If we want to drop a database called "db-name". we have to escape the database name which contains the hyphen by using double quotation marks.

DROP DATABASE "db-name";

Resource link here here

How to kill a process on localhost port on Ubuntu & Windows

eddiejpot — Wed, 19 May 2021 15:04:49 +0000

We'll be using port number 3000 as the example

Ubuntu

Option 1:

Step One:
Get the process id

sudo netstat -lpn |grep :3000

You will get an output similar to this

tcp6  0  0 :::3000    :::*    LISTEN    1234/node

Step Two:
Now that you have the process id - which is 1234 in this example
Kill the process using the code below

kill -p 1234  OR  kill -9 1234

Option 2:

fuser -k 3000/tcp

Windows

Step One
Open up cmd.exe (we may need to run it as an administrator, but this isn't always necessary). Run the below command:
netstat -ano | findstr :<PORT>

netstat -ano | findstr :3000

The arrow shows the PID (process identifier). Locate the PID of the process that's using the port you want.

Step Two
taskkill /PID <PID> /F

taskkill /PID 4692 /F

Step Three
You can check if the operation was successful by re-running the command in "Step 1". You shouldn't see any more search results for that port number.

Where to store SSH key (For Windows) 🔑

eddiejpot — Mon, 10 May 2021 06:19:26 +0000

Prerequisites

Windows Subsystem for Linux (WSL) is installed
For this example we will use the Ubuntu Linux distro/distribution.
Visit this link to rocket academy to find out more about WSL

Step 1: Understand how to access Linux On Windows

Method 1: Using the file explorer

Type \\wsl$\ into the file explorer. This will direct you to the location of the Ubuntu folder.
Navigate to your linux folder. Ubuntu -> Home -> <LINUX USERNAME>

Method 2: Using the WSL terminal

# This command navigates to the linux folder

cd ~/

# This command lists the files that are in the linux folder

ls -a ~

Step 2: Create .ssh folder (this is where we'll put the ssh key)

Notes: If this is your first time accessing this folder, you probably do not have a folder for ssh files and will have to create your own.

Method 1: Using the file explorer

Create a folder in your linux folder and name it ".ssh"
Done! Now you can put the key pairs in this folder

Method 2: Using the WSL terminal

# 1. Check if you have a .ssh folder. If you don't have an ssh folder it'll return "No such file or directory"

ls ~/.ssh

# 2. Create a folder called .ssh 

mkdir ~/.ssh

# 3. Copy any key pairs you need into this folder
# Note: You have to be in the same directory as the file you want to copy
# syntax: cp <FILENAME> ~/.ssh

cp my-aws-ec2-keypair.pem ~/.ssh