Learn Chrome, Python and Xstream

Optional chaining ?. in javascript is a new feature introduced in ES2020. Optional chaining changes the way properties are accessed from deeply nested objects. It fixes the problem of having to do multiple null checks when accessing long chain of object properties in javascript.

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

Optional Chaining

Neural networks, with Keras, bring powerful machine learning to Python applications. They can answer questions like “How much traffic will hit my website tonight?” or answer classification questions like “Will this customer buy our product?” or “Will the stock price go up or down tomorrow?”

In this course, we’ll build a fully connected neural network with Keras. This is the most basic type of neural network you can create, but it’s powerful in application and can jumpstart your exploration of other frameworks. 

We’ll start the course by creating the primary network. Then we’ll:

- build and configure the network, then evaluate and test the accuracy of each
- save the model and learn how to load it and use it to make predictions in the future
- expose the model as part of a tiny web application that can be used to make predictions

You don’t need to know a lot of Python for this course, but some basic Python knowledge will be helpful. Enjoy!

Python is a widely used dynamically typed programming language. It allows for many different programming paradigms including object-oriented, imperative, functional programming, and procedural styles.

python

Fully Connected Neural Networks with Keras

Chrome DevTools are incredibly useful for a frontend developer, sometimes we spend more time using them than our text editor of choice.

That's why it's so important to understand this tool better - those quick lessons will teach you things that will help you to become a more effective developer.

You will learn how to:

- **Use (experimental) CSS Overview to learn all about CSS used on a page in a minute**
- **Style console.log messages with CSS** - a _crucial_ skill for any senior developer (j/k)
- **Debug your code (on production and local environment) with logpoints**
- **Run a Lighthouse audit of your site**
- **Choose accessible colors for your website that have an AAA contrast ratio rating**
- **Force a DOM element state in Chrome DevTools**
- **Use Console utilities to make debugging easier**
- **Copy a network request as fetch or cURL with Chrome DevTools**

Have fun!

The Chrome Developer Tools (DevTools for short), are a set of web authoring and debugging tools built into Google Chrome.

chrome-devtools

Chrome DevTools tips & tricks

In Introduction to Python, we will start at the beginning: Installing python 3 and using virtual environments. With a working environment, we will learn how to manipulate strings and numbers, and gain working knowledge of data structures and flow control. We will build on that by introducing modules and classes and learn how to interact with our python applications using command line switches, console input and files.

At the end of this course, you’ll have a great working knowledge of Python, fully capable of creating your own Python projects from scratch or jumping into an existing application with the capability to read, understand, and contribute to the application.

Check out these [**community notes for this course on Github**](https://github.com/eggheadio-projects/introduction-to-the-python-3-programming-language-notes).

Introduction to the Python 3 Programming Language

Artificial intelligence. Machine learning. Bots. Computers learning and communicating with us to do our bidding. But, where do you start? How do you get a machine to even begin to understand what you speak or type at it? There are several common machine learning algorithms that will help us begin to answer these questions.

In this course we’ll learn about common machine learning algorithms that don’t require implementing a neural network. We will not be going too much into the math behind them, but instead learn what each algorithm is good for, and how to train them. We'll also learn about a few metrics for evaluating models.

We’ll implement these in Python using `scikit-learn` using `scikit-learn`’s built-in data sets. The focus of this course is on implementation and a high-level understanding of these algorithms. 

We'll look at a few ways to evaluate our models, for both classification and regression models. We'll touch on mean squared error and coefficient of determination (for regression), and accuracy score, logarithmic loss, confusion matrices, and classification reports (for classification). 

Python 2.7 is used in the lesson videos but the code provided has Python 3 available. The only breaking change is the `print` statement API.

For additional information on installation, vocabulary, and common errors visit the `README.md` to the course code attached to each lesson.

Simple and efficient tools for data mining and data analysis

scikit-learn

Introductory Machine Learning Algorithms in Python with scikit-learn

AWS Amplify allows developers to create, configure, and deploy Serverless APIs and functions directly from their front-end environment.In this collection, you'll learn how to deploy various types of APIs and functions using the Amplify CLI. You'll also learn how to share code among various functions using Lambda layers and schedule functions to run at an interval to implement Serverless cron jobs.

Up and Running with AWS Amplify Functions

In this course we’ll take a deep look at the Elements panel in the chrome devtools. We’ll step through each button and tab on this panel and discuss how to use them to interact with your web application as it runs.

Debug the DOM in Chrome with the Devtools Elements Panel

This course examines the Sources panel in the Chrome DevTools, which allows you to see what files are responsible for the various things on the screen. Bundled into this panel, though, is the single most useful tool for any JavaScript developer - the JavaScript Debugger. We’ll use the Debugger to inspect JavaScript as it runs, allowing you to watch (and even interact with) the state of your application as it runs in ways that’ll blow your mind if you’ve mostly used console.log to debug your applications to this point. 

Debug JavaScript in Chrome with DevTool Sources

This course will examine the Network panel in Chrome DevTools. We’ll step through the request log, examining the various properties exposed. We’ll talk about timing, filtering, throttling and generally using the network panel to better understand the ways in which our applications exist within a connected context.

Debug HTTP with Chrome DevTools Network Panel

This is a small collection of videos to help you get familiar with Chrome browser's performance oriented developer tools.
In this collection, learn how to record a performance profile, tweak the settings to get the most relevant profile and finally a look into the different sections of the performance data visualisation.

Basics of Chrome's Performance Devtools

Anything related to JavaScript performance

Javascript Performance

Learn how to create tuples in Python. The videos in this collection will also cover more advanced features of tuples

The Ins and Outs of Python Tuples

ASP.NET is an open source web framework for building modern web apps and services with .NET. ASP.NET creates websites based on HTML5, CSS, and JavaScript that are simple, fast, and can scale to millions of users.

asp-net

ASP.NET Core SignalR can push events from the server into your Client Application. In this video we will build a client side Todo app with Angular which consumes events from a ASP.NET Core SignalR backend to see how we can consume and synchronize data between our client side Angular Applications.

Consume ASP.NET Core SignalR values in an Angular Application

Sometimes you get strings instead of objects and you have to parse them out. Here's an example where the raw data I got from a Twitch chatbot message wasn't useful to me until I parsed it into a dictionary.

Turning a key/value string into a dictionary in Python

The axe browser extension (for Chrome and Firefox) is an immensely helpful tool for auditing web pages for accessibility defects.  This extension is powered by the same rules engine developed by Deque Labs in their axe-core open source library which also powers the react-axe development tool.  Each reported defect offers a ton of information about the defect, why it's a problem, severity level, groups impacted and ways to fix the defect.  This can be a great resource for learning more about how to write accessible code.

## Resources
* [Chrome browser extension](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd)
* [Firefox browser extension](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/)

Use the axe Browser Extension to Audit a Web Page for Accessibility Issues

WAI-ARIA, the Accessible Rich Internet Applications Suite, defines a way to make Web content and Web applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with Ajax, HTML, JavaScript, and related technologies. 

aria

tota11y is a great tool to add to your accessibility auditing toolkit.  tota11y is a browser extension available for Chrome and Firefox that helps visualize accessibility violations (and successes), while educating on best practices.  It can make for a really helpful supplement to other accessibility auditing tools.

## Resources
* [About tota11y](https://khan.github.io/tota11y/)
* [Chrome browser extension](https://chrome.google.com/webstore/detail/tota11y-plugin-from-khan/oedofneiplgibimfkccchnimiadcmhpe?hl=en)
* [Firefox browser extension](https://addons.mozilla.org/en-US/firefox/addon/tota11y-accessibility-toolkit/)

Use tota11y to Visualize Accessibility Issues

A modern web browser owned and maintained by Google.

chrome

It's very important to experience our web applications using the tools and techniques that our users are using. Many of our users out there may have vision impairments and may use tools to help them see better. Learn how to use a High Contrast browser extension to see your web application the way many of your users may be seeing it.  You may discover that a lack of contrast between foreground and background colors will cause things to be hard to see or even invisible in certain High Contrast tool settings.

## Resources
* [Chrome browser extension](https://chrome.google.com/webstore/detail/high-contrast/djcfdncoelnlbldjfhinnjlhdjlikmph)

Use a High Contrast Browser Extension to Find Color Contrast Accessibility Issues

screen-reader

We can find issues with heading levels by utilizing our accessibility auditing tools.  The library react-axe, as well as the browser extension axe, will report any findings concerning heading levels.  The browser extension tota11y will annotate all heading levels on a page and show any in red that have issues.  Finally, we can check the Rotor in VoiceOver in Safari.  The Rotor should have a Headings menu and will list in order all of them that are found on the page.  If headings are missing or inappropriate this will help us find them as well.

Test for Heading Level Accessibility Issues

Similar to Landmark Regions, Heading Levels are used by web browsers, plug-ins, and assistive technologies to provide in-page navigation.

## Rules
* Each page should have at least one `<h1>`
* Pages should be structured in a hierarchical manner
    * `<h1>`: being the most important (usually page titles or main content heading)
    * `<h2>`: usually major section headings
    * `<h3>`: sub-sections of the `<h2>`
    * and so on
* Do not skip heading levels - always follow consecutive order
* Do not use text formatting, such as font size or bold to give the visual appearance of headings.  
    * Use actual heading (`<h1>` - `<h6>`) for all content headings
* Do not use heading levels to achieve visual results only

## References
* https://webaim.org/techniques/semanticstructure/
* https://www.w3.org/WAI/tutorials/page-structure/headings/

Correctly Define Heading Levels of a Web Page

The pluggable linting utility for JavaScript and JSX.

eslint

We have a number of options to use when testing for accessibility issues concerning alternative text for images.  The react-axe library and axe browser extension will both report when an image is missing alternative text.  The tota11y browser extension will annotate any images that are missing alternative text.  Running eslint with the eslint-plugin-jsx-a11y plugin installed will report on any `<img>` elements missing an `alt` attribute.  Finally, we can use a screen reader to actually hear what is read when an image has focus.

Test for Image Alternative Text Accessibility Issues

Images must have text alternatives that describe the information or function 
represented by them so they can be read and understood by those using screen readers.

## Alternative text for images
* All `<img>` elements should have an `alt` attribute provided
    * When not provided many screen readers will fallback to reading the file name instead
* The `alt` value should not include words like _“image”_, _“picture”_ or _“icon”_
    * Screen readers are already announcing that the element is an image
* Images that are decorative only and provide no information or function to the page should be hidden from Assistive Technologies by providing an empty `alt` attribute (`alt=””`)

## References
* https://www.w3.org/WAI/tutorials/images/
* https://www.w3.org/WAI/tutorials/images/decision-tree/
* https://www.w3.org/WAI/tutorials/images/tips/
* https://www.w3.org/WAI/tutorials/images/informative/
* https://www.w3.org/WAI/tutorials/images/functional/
* https://www.w3.org/WAI/tutorials/images/textual/

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