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

chrome-devtools

Learn Chrome-devtools

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

Debug Computed Accessibility Properties with Chrome Dev Tools

In this lesson, we use the element inspector in Chrome to test and improve our contrast to meet WCAG AA Contrast Ratio Standards.

Resources:
- [WebAIM - Contrast and Color Accessibility](https://webaim.org/articles/contrast/)

Debugging Accessible Contrast with Chrome Dev Tools

Lighthouse is a tool that analyses web apps and web pages, collecting modern performance metrics and insights on developer best practices.

It's built directly into the Chrome DevTools and in this quick lesson we're going to learn how to run the audit, how to read its results and why you should always run the Lighthouse audit in Incognito mode.



Run a Lighthouse audit in Chrome Devtools

Sometimes you encounter a backend issue which seems to occur only on your computer, with a very specific sets of headers, cookies etc. Because of that, it's useful to have a way of easily sharing network requests sent by your browser with other members of your team.

In this quick lesson we're going to learn how to copy a network request as `fetch` (so we can test it in the Chrome DevTools console/in a node.js script) or as cURL (so we can test it in a terminal).

Copy a network request as fetch or cURL with Chrome DevTools

Sometimes when debugging our CSS styles it's useful to be able to see what a DOM element is going to look like in a given state (e.g. `:focus`, `:active, `:hover`) etc.

Unfortunately it's not possible to both hover over an element and debug it in Chrome DevTools at the same time (since we only have a single cursor!).

In this quick lesson we're going to learn how to address this problem by explicitly forcing an element state to `:hover` with DevTools

Force a DOM element state in Chrome DevTools

In this lesson, we explore using Chrome's DevTools to detect unwanted visual instability on a page.

We can do this using the new "Experience" heading under recorded "Performance" metrics.

To truly see the impact of "[Cumulative Layout Shift](https://web.dev/cls/)", we can make use of DevTools' "Network throttling" feature to see any visual instability with the naked eye.



Use Chrome DevTools to Detect Cumulative Layout Shift

Check out the new and currently experimental "CSS Overview" feature in Chrome's DevTools.

Use it to get an overview of details such as colors, fonts, media queries, and even unused declarations.

Explore a Site's CSS with Chrome DevTools CSS Overview

Good accessibility is crucial in modern web apps. Keyboard navigation plays an important role in that undertaking. In this lesson we're going to explore how we can use the Chrome Devtools to easily debug the current active element on our DOM.

Use Chrome Devtools to debug the current active DOM element

Angular is a development platform for creating applications using modern web standards. Angular includes a wealth of essential features such as mobile gestures, animations, filtering, routing, data binding, security, internationalization, and beautiful UI components. It's extremely modular, lightweight, and easy to learn.

angular

Even though the default scoped styles in Angular components are really useful, sometimes we do want to apply styles across the whole app. We may also want to make classes available globally. Luckily, Angular provides a nice way to do this in the `styles.css` file.

Add Global Styles in Angular

In other frameworks, CSS modules and CSS-in-JS are both quite popular. One of the reasons for this is the ability to add scoped styling to your app. This prevents inadvertently overwriting styles due to a shared global class somewhere. You won't hear much about these options in the Angular community, and that's because Angular comes with a scoped CSS option right out of the box. In this lesson, I'll show you how this works.

Use Scoped Component Styles in Angular

Sometimes we need to pass data from a child component to a parent component. We could pass the source down to the child as an input and modify it there, but that's not a good practice. In Angular, we can use Outputs and EventEmitters to accomplish this instead. The child component emits an event with the data that the parent listens for. The parent can then process the event data however it needs to. In this video, you'll learn how to do just that with a reactive form that needs to send its value up to its parent component.

Communicate Between Components with Outputs & EventEmitters

Miscellaneous one-off lessons on debugging, productivity hacks, and JavaScript tricks.

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

Tips and Tricks

Sometimes you'd like to measure how two implementations compare in regards to run time.  In this lesson you will learn how to quickly do this using Console.time and constole.timeEnd.

Benchmark functions runtime in chrome console

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

express

In this lesson we will learn how to see your node server's code in chrome dev tools and also to add debug points to debug your nodejs app easily.

Debug a NodeJS App in Chrome Dev Tools

Frontend runtime optimization is heavily impacted by rendering.  Understanding the way the JS engine and the browser work is crucial for optimizing applications and understading how to avoid performance pitfalls.
This collection explains about the Critical Rendering Path, performance bottlenecks and practical solutions.

Critical Rendering Path

When building a web app, sometimes we need to approach it top-down. Modern browser devtools allow us to set breakpoints not only on the JS code but also on the DOM as well, so we can easily pin down which lines of code are to be executed deep inside the code base, by pausing the execution based on DOM changes.

In this lesson, we will learn how to set and remove DOM breakpoints in Chrome DevTools.

Set and remove DOM Breakpoints

When the contrast between foreground and background colors is not sufficient it can be hard to distinguish outlines, borders, edges, and details and text can be hard to read. The minimum recommended contrast ratio is 4.5:1 for most text. Very large text (120-150% larger than the default body text) can be slightly lower at 3:1. 

The contrast ratio of 4.5:1 was chosen because it compensates for the loss in contrast sensitivity usually experienced by users with vision loss equivalent to approximately 20/40 vision which is commonly reported as typical visual acuity of people at about age 80.

## References
* https://webaim.org/articles/contrast/
* https://webaim.org/resources/contrastchecker/
* [Accessible Color Picker Chrome browser extension](https://chrome.google.com/webstore/detail/accessible-color-picker/bgfhbflmeekopanooidljpnmnljdihld?hl=en-US)
* https://color.review/

Use Sufficient Color Contrast in Web Page Design

The pluggable linting utility for JavaScript and JSX.

eslint

Our accessibility auditing toolkit makes it very easy for us to test for any form controls that are missing labels or are not correctly associated with their labels.  Running Eslint with the eslint-plugin-jsx-a11y installed will show us any form controls with missing or unassociated labels.  Running react-axe or using axe to audit a web page will similarly list any of these findings.  Finally using tota11y we can annotate any form controls on a page that are missing labels.  This is definitely some of the lower hanging fruit that we can easily find and fix when making our applications accessible!

Test for Form Control Label Accessibility Issues

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

Using our accessibility auditing toolkit we can find issues concerning landmark regions in our web application.  The react-axe library will report findings in the JavaScript console of the browser.  We could also run the axe browser extension to see the same results.  The tota11y browser extension will annotate any landmark regions on the page and therefore if none are annotated it may indicate that they aren't any (_NOTE: tota11y will only annotate landmark regions using aria roles and not those using HTML5 elements_).  Finally using the VoiceOver Rotor in Safari will show us whatever landmark regions have been defined in the Landmarks menu. 

Test for Landmark Region Accessibility Issues in React

Labeling inputs, elements, and widgets add context and clarity for assistive technology such as screen readers.  Elements of a `<form>` such as `<input>` or `<textarea>` or `<select>` should be labelled by using a `<label>` element.  Placeholder text can be used in addition to a label but should not be used in place of a label as not all assistive technologies respect placeholder text.

Ensure Form Controls have Accessible Labels

Mock Service Worker is an API mocking library that allows you to write client-agnostic mocks and reuse them across any frameworks, tools, and environments.



Mocking WebSocket APIs with Mock Service Worker


When attempting to load the same module twice in JavaScript you'll hit a cache and code won't re-run. In scenarios where you actually do want to have state in your modules, you'll have to use a cache-busting technique by passing a query parameter to a dynamic import. This lesson walks through how to add a query parameter, how to add the appropriate types for loading dynamic modules in TypeScript, and when these techniques are valuable.

Import the Same JavaScript Module Multiple Times with Cache Busting



The include keyword in GitHub Actions empowers you to add custom variables to your matrix strategy, providing flexibility beyond standard configurations. In this video, we'll explore how include allows you to define specific combinations of variables, enhancing control over your workflow runs. You'll see how this feature enables you to tailor jobs for unique environments or scenarios not covered by the default matrix options. By leveraging include, you can efficiently manage complex build processes with greater precision. This technique helps you streamline your CI/CD pipeline, making it more adaptable to your project's evolving needs.

Use GitHub Actions Matrix Include for Complex Job Configurations

While running `zod` schema validation agains domain-rich objects, the error message saying that _a string is not a number_ might not be really useful.

Especially, when you need to provide a meaningful feeback to the user, e.g. after they have submitted a form with lots of data.

`zod` allows to customize messages on a very granular level. We can also extract repeatable customization to `zod` error maps.

Finally, in order to process an error message further (e.g. display it to the user), we need to handle the `zod` validation errors effectively. Especially, when a big object validation has failed and we could receive a handful of errors.

That's what we learn in this lesson. 🔥

Customize zod Error Messages and Handle zod Errors Effectively

customize zod validation messages, customize zod schema property messages, reuse error maps across different schemas, navigate through zod error objects

You might want to run `zod` schema checks in different styles.

Sometimes you prefer to conditionally throw the error - that's what `parse` does. But another time you'd prefer to receive a `boolean` property that determines whether the validation was successful or not - and perform further actions accordingly.

Additionally, the error-throwing API of `parse` works extremely well with [TypeScript assertion functions](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions). Their combination is just... perfect! 👌

That's what we learn in this lesson.

Use parse and safeParse Runtime Type-checks with zod

use zod parse function to conditionally throw ZodError, use zod safeParse to get a boolean value and run typescript type guard over success property

In this lesson we learn that TypeScript cannot guarantee correct shapes of responses. That's due to TS performing checks in compile-time, while the response will be availbale in runtime - when TS doesn't exist anymore.

In some situations, such as HTTP requests, runtime type checks such as `zod` are essential for providing quick feedback around data-related errors.

Understand where are the possible mistakes to make while using TypeScript with HTTP calls. Use `fetch` and `axios` along with `zod` schema checks.

Also, note that similar mistakes or mistakes could happen while using web storage (e.g. `localStorage`)

Validate HTTP API Response with zod, fetch and axios

use zod as an HTTP response validation tool along with fetch and axios in order to make sure that the response has expected data structure

In this lesson we learn that the `zod` schemas become the single source of truth.

We shall not update TypeScript types manually, since they are generated automatically from the schema.

Same with validation functions.

Whenever the schema changes, all the rest will update accordingly. It's an important mind shift.

Treat zod Schemas as Single Source of Truth

Zod Schemas are the single source of truth for both typescript types, and interfaces - and runtime validation functions. Schemas should be updated first.

`zod` is powerful, but writing the schemas manually for existing JSON objects, especially big ones, can be time-consuming.

But that's what `quicktype` is for! You can get 80% work done instantly! 🥳

Depending on your need - whether you want to automate the process, or do it just one time, you can:
- use an online app
- use an IDE extension
- run a CLI script
- generate a script to be executed within CI/CD environment/tooling

And this is what we learn in this lesson! 🔥🔥🔥

Get started with zod quickly!

Generate zod Schemas Automatically using Quicktype App, Extensions and Scripts

Use quicktype app, extension or scripts to automatically generate zod schemas from existing json files. Save time and get started with zod quickly!

`zod` is a powerful library allowing to run runtime type-checks.

It's complementary to TypeScript, which does type checks in compile time.

In this lesson we create few schemas that represent primitive type values, along with `zod` utilities which make these more precise. We also create object schemas and nest one inside another.

All schemas are being validated against example values. We analyze how to interpret error messages in case of failures.

Perform Runtime Type-checks on Primitives and Objects with zod

Create zod schemas to validate primitive type and object type values in runtime. Analyze the errors to see how a value doesn't correspond to schema expectations


Using Cursor Chat, you can easily reference an entire directory of files and ask it to generate anything based on those files. This opens up the possibility of using your current code as a reference guide to create new code that follows existing patterns. With this approach, the result can be a polished prompt you can use with any AI to generate consistent and reliable output.

Focus less on crafting the perfect prompt upfront - what matters most is testing and iterating based on the AI's responses. The more results you see from the prompt, the more you can reinforce the good results and prune out the bad results until your prompt is polished enough that you can rely on the prompt to give you consistent quality results.


Chrome DevTools

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