AWS - Using Named Profiles

Getting the Most of Named Profiles

The AWS CLI supports using any of multiple named profiles that are stored in the config and credentials files. You can configure additional profiles by using aws configure with the –profile option, or by adding entries to the config and credentials files.

The following example shows a credentials file with two profiles. The first is used when you run a CLI command with no profile. The second is used when you run a CLI command with the –profile user1 parameter.

~/.aws/credentials (Linux & Mac) or %USERPROFILE%\.aws\credentials (Windows)


[Read More]

I am a Super User

Is Learning more useful than Knowledge?

Perhaps the greatest misconception I held as a novice computer programmer was that software was about “knowledge”. An important realization I had is that the much more significant skill is actually “learning”. After all, how do those who have knowledge acquire it? Through learning, of course! This is especially true of web development technologies, which seem to evolve much quicker than languages like Java, or C++, for example.

I am a superuser. I have been using the web to find answers and learn new skills my entire life.

[Read More]

Creating Animated GIFs using a Bash pipe

How I create superior-quality GIFs using FFMPEG and ImageMagic

A coding friend asked me recently how I created my superior quality animated GIF demos of running Cypress e2e testing my applications.

I have to confess - this one-liner truly gives me utmost pleasure in life.



  • FFMPEG audio/video swiss-army knife FFMPEG
  • ImageMagic convert - better aGIF generator than FFMPEG ImageMagick
  • Bash command line pipe Bash
[Read More]

BikeStack Mobile

A React Native Application

A performance tracking and data visualization app for bicyclists.

Scan to open

With an Android phone, you can scan this QR code with your Expo mobile App to load this project immediately.

Visit this app at it’s home on (


  • TypeScript
  • Amazon Web Services (AWS)
  • AWS Amplify
  • AWS Cognito user pools (secure user creation and authentication)
  • AWS DynamoDB (highly scalable record persistence)
  • React native navigation
  • Expo

Functional Programming with Ramda.js

React.js library with a focused FP goal



Ramda is a library designed specifically for a functional programming style. It makes it easy to create functional programming pipelines, and never mutates user data. JavaScript’s Array.prototype class has some functionally-flavored methods such as map, reduce, and filter. However, these only operate on arrays. Ramda is described as more generic, being that it can work with strings, objects, and user-defined data types. There are other convenience libraries that allow functional operations on objects, such as lodash, but Ramda is much more functional by design; explicitly eliminating the possibility side-effects, and facilitating a divergence from the very imperative style of JavaScript to a more declarative model of programming.

Composition with Functions

So why would I want to use Ramda when lodash is easier to understand? Ramda allows functions to be used as first-order components.

[Read More]

Integration testing with Cypress

React.js E2E Testing Frameworks


Cypress E2E Integration Testing

The cypress testing framework is an end-to-end integration test framework for React.js, which is quickly surpassing alternatives such as Jest, Mocha, and Enzyme, Chai, and others.

Unit testing had long been an area of React.js where a stark lack of consensus existed. Myriad different frameworks had been available, all with their own selling points. Many developers won over by Cypress are now abandoning this patchwork of other unit testing tools in droves.

[Read More]

Using React Hooks API

An alternative to Redux


The hooks api is a game-changing new framework introduced by the Facebook team in React 16.8. It represents a radical foray into a totally new paradigm of React.js development.

Notes on Hooks

Hooks are like primitive composable components for React. With hooks, instead of using ES2015 classes and complex third party frameworks such as Redux, we can use simple function() expressions throughout.

Functional Programs

They are more functional - essentially they trade the complexity of how classes work for the complexity of how closures work. Hooks are more consistent with functional programming.


I had previously associated side-effects with a negative connotation, but in this context, side-effects are very much intentional. A side-effect, or simply effect is employed anytime we perform a fetch operation or write something out to the console in a class component.


One of the most exciting parts of the Hooks API is the global state functionality. With useState, we have native functionality in React that might finally make it possible to avoid Redux entirely. At long last, React developers can make use of global state without cluttering up our applications with loads of messy connect functions and the 10 pounds of actions, reducers, and lifecycle triggers code it takes to get an ounce of functionality in React.

[Read More]

Using TypeScript with React

How Strong Typing Helps You Spot Errors You Never Knew Were There


So what is Typing anyway?

To understand what TypeScript is, first you must be familiar with the concept of typing. JavaScript developers will probably be aware of the difference between Equality (==) and Identity (===) Operators. These operators differentiate between entities like the string "123" and the integer 123. This is because numbers and characters are fundamentally stored differently in memory. In JavaScript, all variables are declared using the keyword var (or const/let). However, this is not the case in strongly typed languages, such as Java and C, which CANNOT declare any variable without an explicitly defined data type.

JavaScript is ‘interpreted’, not ‘compiled’

A data type is a formalization of the way in which information is represented in a computer system, such as the case with Integers and Strings. Languages such as Java and C are referred to as strongly typed languages, because they depend on these types being defined at compile time, before the high-level language is converted into machine code or byte-code. JavaScript is an interpreted language (it is not compiled) It uses dynamic typing because, as the name implies, JavaScript was created with script-building in mind. Scripts generally automate the execution of code that is exterior to the script itself (such as compiled programs). As JavaScript development has become increasingly complex, there has arisen greater need for more explicit typing. This need was partially met by tools such as PropTypes. However, TypeScript, which was created by Microsoft, is especially helpful for validating the consistency of user-designed data objects.

Type Checking

Type checking is the idea that the shape of a data object remains consistent as it is passed between different parts of a program. TypeScript extends the JavaScript language, making it possible to explicitly define the shape of objects when they are declared, or passed into / returned from a function.

[Read More]

Snapshot Testing with Jest and Enzyme

Unit testing in React


What is Jest?

Jest is a popular Node.js unit testing framework, frequently used with React. Like React itself, Jest is used internally by Facebook as a primary development tool. Jest allows for tests to be run in parallel, greatly increasing efficiency.

Why use tests at all?

Even after you complete an app and get everything finally working, this is always the possibility of future modifications introducing new bugs. Unit testing simply makes it easier to guard against this scenario.

How do I install Jest?

Jest is included with React (and React Native). Otherwise, it can be installed using your package manager of choice

npm install --save-dev jest
yarn add --dev jest
[Read More]

Setting Up Authentication on AWS Amplify

Using Amazon Web Services Console


Creating an AWS Account

It is necessary to provide a payment method (Credit or Debit card) to use AWS, including the free tier. Be careful about this - many people have complained that they end up getting charged surprise fees even though they never intended to go over the data caps for the “free” services.

Creating a Sub-user

While it is possible to use your root AWS account for managing services, this is not recommended. The principle of least access is that no account should have more privilege than is needed. This will limit potential fallout in the case that any of your account keys are breached. Those familiar with UNIX systems understand that the root user is not meant to be used for normal operations, and in AWS it is recommended that you create a sub-user for managing AWS services. This is kind of like having a luxury car that has a “valet key”, which is basically a key that can start the engine, but won’t allow the glove-box or trunk to be opened (to prevent theft).

[Read More]