Reid  Rohan

Reid Rohan

1624865820

TypeScript 4.3: I Object Your Honor!

With the release of TypeScript 4.3, this article discusses TypeScript’s Object-Oriented features and looks at the new features this release brings.

In celebration of TypeScript 4.3, I take a look at TypeScript’s Object-Oriented features and look at the new features this release brings.

TypeScript provides good support for both object-oriented programming and function-oriented programming (I’m not saying functional programming as I don’t want the purists to hunt me down).

In this post, I’m going to review OO support within TypeScript and show the latest OO features provided in  TypeScript 4.3.

I’ll quickly cover:

  • Basic Class Mechanics and the Prototype-based System.
  • Accessibility and Parameter Properties.
  • Inheritance, Types, and Type Assertions.
  • Accessors and 4.3’s support for differing types.
  • ECMAScript Private and 4.3’s extension to methods and accessors.
  • 4.3’s new override keyword.

TypeScript OO Review

Classes, Objects, and Prototypes, oh my!

Object-Oriented Programming in JavaScript has always been a little bit strange and with TypeScript being a superset of JavaScript, some of that funk is still hanging in the air.

The  prototype system for managing classes can feel strange when coming from other object-oriented languages like Java, C#, or C++. In JavaScript, a class actually creates an object in memory, just like any other object, to contain common functionality that all instances of that class share (typically methods). This object is the prototype, accessed via the prototype property from the class and the __proto__ property from all instances.

Prototype System

When we instantiate an object of a class, we actually create a new blank object, but that blank object has a prototype that points to the shared instance so inherits its behavior. The constructor function runs which will typically populate the blank object with properties.

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TypeScript 4.3: I Object Your Honor!
Arvel  Parker

Arvel Parker

1591611780

How to Find Ulimit For user on Linux

How can I find the correct ulimit values for a user account or process on Linux systems?

For proper operation, we must ensure that the correct ulimit values set after installing various software. The Linux system provides means of restricting the number of resources that can be used. Limits set for each Linux user account. However, system limits are applied separately to each process that is running for that user too. For example, if certain thresholds are too low, the system might not be able to server web pages using Nginx/Apache or PHP/Python app. System resource limits viewed or set with the NA command. Let us see how to use the ulimit that provides control over the resources available to the shell and processes.

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MEAN Stack Tutorial MongoDB ExpressJS AngularJS NodeJS

We are going to build a full stack Todo App using the MEAN (MongoDB, ExpressJS, AngularJS and NodeJS). This is the last part of three-post series tutorial.

MEAN Stack tutorial series:

AngularJS tutorial for beginners (Part I)
Creating RESTful APIs with NodeJS and MongoDB Tutorial (Part II)
MEAN Stack Tutorial: MongoDB, ExpressJS, AngularJS and NodeJS (Part III) 👈 you are here
Before completing the app, let’s cover some background about the this stack. If you rather jump to the hands-on part click here to get started.

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systemctl List All Failed Units/Services on Linux

Is there is a command to print list all failed units or services when using systemd on Linux? Can you tell me the systemctl command to list all failed services on Linux?

This quick tutorial explains how to find/list all failed systemd services/units on Linux operating systems using the systemctl command.

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Yoshiko  Jones

Yoshiko Jones

1598195340

How to configure AWS SES with Postfix MTA

How do I configure Amazon SES With Postfix mail server to send email under a CentOS/RHEL/Fedora/Ubuntu/Debian Linux server?

Amazon Simple Email Service (SES) is a hosted email service for you to send and receive email using your email addresses and domains. Typically SES used for sending bulk email or routing emails without hosting MTA. We can use Perl/Python/PHP APIs to send an email via SES. Another option is to configure Linux or Unix box running Postfix to route all outgoing emails via SES.

  • » Remove sendmail
  • » Install postfix
  • » Configuring postfix for SES
  • » Test postfix

Procedure to configure AWS SES with Postfix

Before getting started with Amazon SES and Postfix, you need to sign up for AWS, including SES. You need to verify your email address and other settings. Make sure you create a user for SES access and download credentials too.

Step 1 – Uninstall Sendmail if installed

If sendmail installed remove it. Debian/Ubuntu Linux user type the following apt command/apt-get command:

$`` sudo apt --purge remove sendmail

CentOS/RHEL user type the following yum command or dnf command on Fedora/CentOS/RHEL 8.x:

$`` sudo yum remove sendmail

$`` sudo dnf remove sendmail

Sample outputs from CentOS 8 server:

Dependencies resolved.
===============================================================================
 Package           Architecture  Version               Repository         Size
===============================================================================
Removing:
 sendmail          x86_64        8.15.2-32.el8         @AppStream        2.4 M
Removing unused dependencies:
 cyrus-sasl        x86_64        2.1.27-1.el8          @BaseOS           160 k
 procmail          x86_64        3.22-47.el8           @AppStream        369 k

Transaction Summary
===============================================================================
Remove  3 Packages

Freed space: 2.9 M
Is this ok [y/N]: y

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CentOS Linux 8.2 Released and Here is How to Upgrade it

CentOS Linux 8.2 (2004) released. It is a Linux distribution derived from RHEL (Red Hat Enterprise Linux) 8.2 source code. CentOS was created when Red Hat stopped providing RHEL free. CentOS 8.2 gives complete control of its open-source software packages and is fully customized for research needs or for running a high-performance website without the need for license fees. Let us see what’s new in CentOS 8.2 (2004) and how to upgrade existing CentOS 8.1.1199 server to 8.2.2004 using the command line.

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