Monthly Archives: November 2018

Declared and undeclared variables in functions

ref – https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/var

Declared variables are constrained in the execution context in which they are declared.

Undeclared variables are always global

…even in inner functions

Let’s declare an inner function called ‘inner’. We have an undeclared variable ‘name’.
That name will be declared as a global. It will be accessible by all scopes.

Chat Room using Node

ref – https://socket.io/get-started/chat

setup

Assuming you have node, npm, nodemon/gulp installed.

First, make a directory called DesktopApp. Then start the process of creating a node project.


npm init

Enter your information for the package.json file.

Install Express:

npm install –save express@4.15.2

Server can push messages to clients. Whenever you write a chat message, the idea is that the server will get it and push it to all other connected clients.

Installing mongodb on Ubuntu

ref – https://www.digitalocean.com/community/tutorials/how-to-install-mongodb-on-ubuntu-18-04

Step 1 — Installing MongoDB

Ubuntu’s official package repositories include an up-to-date version of MongoDB, which means we can install the necessary packages using apt.

First, update the packages list to have the most recent version of the repository listings:

sudo apt update
Now install the MongoDB package itself:

sudo apt install -y mongodb
This command installs several packages containing the latest stable version of MongoDB, along with helpful management tools for the MongoDB server. The database server is automatically started after installation.

Next, let’s verify that the server is running and works correctly.

Step 2 — Checking the Service and Database

The installation process started MongoDB automatically, but let’s verify that the service is started and that the database is working.

First, check the service’s status:

sudo systemctl status mongodb