Learn Elixir, Microsoft and Particle

These videos include the introductory steps to writing your first Elixir function and beginning to understand some key concepts in Elixir that make it unique. 

Some of those concepts include:
- the Mix build tool
- project structure
- collections of functions written in modules
- function *arity*
- pattern matching and common uses for it
- the pipe operator

Elixir is a dynamic, functional language designed for building scalable and maintainable applications.

Elixir leverages the Erlang VM, known for running low-latency, distributed and fault-tolerant systems, while also being successfully used in web development and the embedded software domain.

elixir

Getting Started with Elixir

particle

Before powering up the Particle Photon we are going to look at what each of the components are on the board.

Particle Photon Component Overview

Microsoft Windows is a group of several graphical operating system families, all of which are developed, marketed, and sold by Microsoft. Each family caters to a certain sector of the computing industry.

microsoft

For a production Windows server it makes sense to run NodeJS applications as a Windows service.  This way they can be automatically restarted if the server is rebooted.

It also makes it easier to use monitoring tools like datadog to detect if there are issues with the service which is critical for production systems.

Install a Node.js Application as a Windows Service

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

express

To replicate your production application its helpful when developing a local NodeJS Express application is running under SSL. 

There are some web technologies which do not play nicely with standard http and its likely to become more common e.g. Web Push Notifications.

This lesson will show you how to create a local SSL certificate for localhost and then convert it into a format that will work with Express.  It will also show you how to make sure that Chrome will trust it.

This lesson is for Windows as it uses a powershell command, as well as the Microsoft Management Console (MMC)
 

Create Local SSL Certificates for an Express App on Windows

The pipe operator is an easy to use and powerful feature of Elixir. It takes the output from the expression on the left, and automatically passes it as the first argument to the function on the right. This is especially useful when chaining together multiple function calls or data transformations. Using the pipe operator results in code that's easier to read, write and refactor.

Chain Function Calls with the Pipe Operator in Elixir

Flutter allows you to build beautiful native apps on iOS and Android from a single codebase.

flutter

We will setup our first command-line Dart application. We will use the Chocolatey package manager to install the SDK and write our first  program. This will form the basis for future lessons.

Get Chocolatey → https://chocolatey.org/docs/installation

Get the gist of commands → https://gist.github.com/creativebracket/128dafcbbfdc1d6946231a931f95cb1b

Setup your first Dart project on Windows

Learn the various ways to access and enable High Contrast Mode on Windows.

Enable High Contrast Mode on Windows

We should not use color alone as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.  Users may not be able to see/understand the differences in color and require additional indicators.

Along with color, use additional indicators such as:
* typography
* shapes
* grids
* spaces
* and/or allocate more weight to important elements

## References:
* http://www.particletree.com/features/interfaces-and-color-blindness/
* https://www.smashingmagazine.com/2014/10/color-contrast-tips-and-tools-for-accessibility/

Use More than Color Alone to Convey Information in a Web Page

Just about every tool in our accessibility auditing toolkit can help us identify any issues with sufficient color contrast ratio on a web page.  The react-axe library and axe browser extension both report findings on all elements with insufficient contrast ratios.  The tota11y browser extension will annotate any elements with their contrast ratios and color those that are insufficient in red.  

Additionally, we need to use our experience tools to see what some of our users out there may we seeing.  We need to test with high contrast browser extensions as well as the display settings in Windows and Mac.  If our users with visual impairments are using these tools we need to see what our application looks like using them because we may find that under a certain mode some things may suddenly be harder to read or virtually invisible.

## Resources
* https://www.scottohara.me/blog/2019/02/12/high-contrast-aria-and-images.html

Test for Insufficient Color Contrast Accessibility Issues

Bootstrap a new Elixir project using Mix (a build tool included when you install Elixir), with its built in project generation.

Additional resources:
- [Official introduction to Mix](https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html#our-first-project)

Generate a new Elixir project using Mix

Elixir code is organized into groups of functions called modules. You can create your own modules and built on top of predefined modules that are a part of Elixir by default.

Additional resources: 
- [Getting started with Modules and function from Elixir docs](https://elixir-lang.org/getting-started/modules-and-functions.html)

Write a New Function Inside of an Elixir Module

The syntax to pass arguments into functions is akin to many other languages. Elixir functions are uniquely recognized when running based off of the number of arguments passed in (a term called *arity*). This means you can define functions with the same name, so long as a different number of arguments is passed in.

Arity is a key concept to be aware of when reading documentation and writing your own code.

Additional resources:
- [Information about arity](https://elixir-lang.org/getting-started/modules-and-functions.html#function-capturing)
- [Default arguments in functions](https://elixir-lang.org/getting-started/modules-and-functions.html#default-arguments)

Pass arguments into Elixir functions and understand arity

Elixir uses `=` as an operator, but rather than assigning values to variables with it, it *matches* values on the right hand side of the `=` with the left side. This can be used in simple values, more complex data structures, and powerful condition checking.

Put into simpler terms, pattern matching is Elixir's way of assigning variables.

Additional resources:
- [Elixir docs on pattern matching](https://elixir-lang.org/getting-started/pattern-matching.html)

Pattern match values in Elixir

Some common uses for pattern matching in Elixir include checking conditions and passing parameters into functions. It's useful for pulling out only specific variables from collections of data.

Additional resources:
- [Elixir docs on pattern matching](https://elixir-lang.org/getting-started/pattern-matching.html)

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