Learn Chai, Flexbox and Flow

The specification describes a CSS box model optimized for user interface design. In the flex layout model, the children of a flex container can be laid out in any direction, and can “flex” their sizes, either growing to fill unused space or shrinking to avoid overflowing the parent.

flexbox

With just a handful of CSS properties, we can create an intrinsically responsive photo gallery using flexbox. This is accomplished by setting our preferred width as the `flex-basis` value and allowing items to both shrink and grow. The use of `object-fit: cover` on images allows them to fully fill up the list item without distortion or overflow. We finish the gallery with a small animated effect that alters `opacity`.

Create an Automatically Responsive Flexbox Gallery

CSS Grid and Flexbox are very useful tools for providing the overall layout of a page.  I take a specific design and create the high level layout using css grid and then arrange an individual section using flex box.

Layout a webpage using css grid and flexbox

See how to use flexbox to layout variable-width content in columns, and take advantage of `justify-content` to keep flex children center-aligned on smaller viewports. We'll also learn how `margin` can be applied to resolve for lack of a well-supported `gap` property in flexbox. At the end of the lesson, we'll have styled both the "Subscribe" section and the site footer.

Use Flexbox to Responsively Layout Variable-Width Content

It's tempting to pick up a framework which has preselected flexbox or grid as the layout tool of choice, but it's important to learn when and why to use each method. This leads to slimmer stylesheets which results in better site performance, and less likelihood for "hacks" to make one method do what the other does inherently better. 

Throughout this collection, we will be progressively styling a responsive landing page template while building your knowledge on when to select grid or flexbox for any layout scenario. Spoiler alert: sometimes the best solution is using both!

Create a Landing Page with CSS Grid and Flexbox

Learn the fundamental difference between CSS grid and flexbox layout, and create utility classes for each `display` value. Then begin to apply and expand these concepts to style the landing page navigation.

Choose Between Grid or Flexbox for CSS Layout

We have a parent HTML element that takes up the height and width of the page. We will make that parent element into a flex container, and then vertically center its child element using `align-items: center;`. Finally, we'll use `justify-content: center;` to horizontally center the element.

Center an Element Horizontally and Vertically using Flexbox

Flexbox is a powerful way to layout HTML so that elements can grow to fit the size of their container.  It can also control how the elements are positioned within a flexed container.  

Once you start thinking in `rows` and `columns`, you can control almost any flexed layout with just a few simple flexbox layout primitives.

Get Started with Flexbox CSS Layouts

To stretch individual elements to fit the given space, we can set the `flex-grow` or `flex` attributes to any integer.  Other surrounding elements will grow proportionally to their `flex-grow` or `flex` attributes.

Proportionally Grow a Flexed Element by Setting `flex-grow` or `flex` Styles

To set the wrap settings of elements inside of a container, we can set the `flex-wrap` css attribute.  The most common values are: `nowrap`, `wrap`, or `wrap-reverse`

Wrap Elements Inside of a Flexed Container with `flex-wrap`

We changed the axis layout with 'justify-content', and the "off axis" layout is controlled by 'align-items'.  The most common values are `flex-start`, `flex-end`, or `center`.

Change the off-axis Alignment of a Flexed Container with `align-items`

We can space items inside of a flexed component in the "on-axis" direction, with `justify-content`.

Justify content can take the following values: `flex-start`, `flex-end`, `center`, `space-between`, `space-around`, or `space-evenly`

Change the Spacing of Flexed Components with justify-content

After setting `display: flex` on a parent element, you can use `flex-direction` to switch the container to be either a `row` or a `column`.

We also switch the body between `row` and `column`.

Flex into a Row or a Column with flex-direction

React is one of the web’s most popular frameworks for building JavaScript applications. 

If you know what you’re doing, React can drastically simplify how you build, use, and maintain code.

Whether you’re a React newbie or you’re ready for advanced techniques, you can level-up with egghead. Explore our in-depth courses, lessons, and community resources to build more powerful applications and crack open your career.

react

In this lesson we are going to add types throughout our basic todo list component. This includes type checking the component props, local state, and property methods. 

Type Check React Components With Flow

In this lesson we are going to take a React and Redux application and add flow types throughout. This includes type checking a react component, a reducer, some actions, and a connect method. 

Type Check Redux Apps with Flow

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

chai

In this lesson, you will learn how to verify your API server is returning HTTP 400 responses when clients submit incorrect data. Returning HTTP 400 ensures that your clients are notified of the incorrect usage. Testing for them ensures your API returns errors instead of incorrect responses when supplied with incorrect data.

Test for HTTP 400 responses with Mocha and Chai

In this lesson, we will use Chai's request method to test our Node application's API responses.
By the end of this lesson, you will know how to:
- install the prerequisites to use mocha and chai in your application
- test for HTTP status response codes
- test for a string of text on a page
- test for a json response and validate the properties of the object
- write tests that not only verify the response of your application, but the behavior as well


Test Node RESTful API with Mocha and Chai

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

mocha

Writing great ES6 style Promises for Node.js is only half the battle. Your great modules must include tests as well to ensure future iterations don't break them. In this lesson, I show you a simple ES6 Promise in Node.js, then walk you through creating tests in Mocha using chai and chai-as-promised to test both resolve and reject methods.

Testing ES6 Promises in Node.js using Mocha and Chai

flow

We'll go over some of the built-in types in Flow and how to add them to our projects by adding type annotations to our variables in JavaScript. We'll also learn about type mismatch errors when we give a variable a value that doesn't match its type annotation and how to fix it.

Primitive Types in Flow

Flexbox makes it easier to create layouts that can adjust depending on the content that is added and the space available. In this lesson we look at a couple real-world applications of Flexbox in an application and website.

Using Flexbox in Websites and Applications

Nuclide is the IDE Facebook employees use to write React code. But setting it up to use Flow type checking and Eslint to lint files on the fly is tricky. This video shows you how. 

Setup Nuclide to use Flow and Eslint (Mac)

React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.

react-native

React Native utilizes flexbox for layout, and you can apply styles inline, or via external stylesheets. We will learn about both approaches, and create some basic styles for a native application.

For getting your application setup, you might want to checkout [this lesson](https://egghead.io/lessons/react-react-native-up-and-running?course=react-native-fundamentals&from=react-applying-styles-in-react-native)

Applying Basic Styles in React Native



Discover how to harness the power of Cursor IDE's Composer Agent feature to optimize your code. In this lesson, you'll witness an AI agent doing all the work to generate test suites, implement performance benchmarks, and create optimized function variations - all without writing a single line of code. You'll learn how to validate performance improvements through data-driven benchmarking, ensuring that optimizations are backed by concrete metrics rather than speculation. This hands-on demonstration showcases a groundbreaking approach to automated function development that combines the precision of test-driven development with the efficiency of AI-powered optimization.


Agent-Driven Development in Cursor: Testing, Benchmarking, and Optimizing Functions

This course is aimed for using `zod` effectively in projects based on TypeScript (both browser and node.js). The benefits you gain with this course is not just simply coding, but also understanding when/why/how should you perform runtime validation.

`zod` is the missing piece to TypeScript's capabilities, which can guarantee type-safety only in compile-time.

`zod` can be used whenever the compiler cannot guarantee what happens in runtime. And... it's a very frequent usecase, such as HTTP calls, websockets, etc.

In this course you get quickly up and running by:
1. using `zod` with primitives and objects
2. adapting `zod` quickly to existing projects thanks to automatic generators
3. changing the strategy frm type-first to schema-first
4. using error-throwing `parse` or non-error-throwing `safeParse` basing on your needs
5. applying `zod` to the most common usecase - validating API responses
6. handling errors the most convenient way (out of many!)

Take advantage of runtime validation with `zod`. Take advantage of the detailed lessons in this course 🔥

Effective Runtime Type Checks with Zod


Cursor can now automatically run commands in the terminal and walk step-by-step towards building out your entire project. You give it a goal, then it will suggest the commands you need to run and the files that you need to create and you can work with it to achieve what you're building. This lesson does a quick walkthough of using a Cursor Agent to build a project from scratch and guide it along the way. Cursor Agents definitely feel like a sneak peek at the future of programming!

Cursor Agents Initial Impressions - Allow an AI to Build Your Entire Project

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


While using anonymous functions might seem convenient, they can create difficulties when trying to identify performance bottlenecks during profiling. This lesson will demonstrate how named functions make it easier to pinpoint and address performance issues, ultimately leading to more efficient and debuggable code. Learning this practice will greatly improve your ability to locate and fix performance issues in complex projects.

Always Name Functions in JavaScript


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

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