 Courses from Andre Staltz

RxJS is a library for composing asynchronous and event-based programs by using observable sequences. 


rxjs

While there are many cases where we often believe that an RxJS Subject is necessary, there is a way of avoiding them. In this lesson we will see how to identify the underlying source of data and convert it into an Observable, essentially eliminating the use of an error-prone Subject. 

Convert an underlying source of data into an Observable

While flatMap is popular and convenient for flattening higher-order Observables, it can introduce new kinds of bugs related to subscriptions. In this lesson we will see how switchMap is a sensible default that avoids common bugs.

Use switchMap to avoid leaks when flattening

The do() operator allows us to perform side effects in the chain of operators. However, there are limited use cases for do(). We will learn what those use cases are and how to use subscribe() most of the times.

Move important side effects from do() to subscribe()

The Observable in RxJS is a JavaScript class, and can be extended. In this lesson we will learn about those cases where extending the Observable class becomes a problem, and what cases where it makes sense to extend it.

Know when to extend the Observable class

Eventually you will feel the need for pausing the observation of an Observable and resuming it later. In this lesson we will learn about use cases where pausing is possible, and what to do when pausing is impossible. 

Implement pause and resume feature correctly through RxJS

This lesson will highlight the true purpose of the zip operator, and how uncommon its use cases are. In its place, we will learn how to use the combineLatest operator.

Replace zip with combineLatest when combining sources of data

Operators like publish(), refCount(), share() make it easy to convert a cold Observable to a hot one, and are often necessary to get some feature done. In this lesson we will learn when exactly do we need to convert to hot, and when can we leave the Observable cold.

Make Observables hot only where necessary

The use of RxJS Subjects is common, but not without problems. In this lesson we will see how they can be usually safely replaced with plain Observables.

Convert RxJS Subjects to Observables

In this lesson we will learn about potential problems that may arise when using Observable.create, a low-level function for creating Observables. In its place, we will use easier helper functions that create Observables in a safe manner.

Replace Observable.create with Observable creation helpers

Manually unsubscribing from subscriptions is safe, but tedious and error-prone. This lesson will teach us about the takeUntil operator and its utility to make unsubscribing automatic. 

Use takeUntil instead of manually unsubscribing from Observables

In this lesson we will learn how to replace excessive subscribing and Subject emissions with simple uses of the map operator, simplifying our code and making it less bug-prone. 

Use the map operator instead of firing events on a Subject

We are going to see how to avoid virtually any case of a subscribe happening inside another subscribe by replacing it with a flattening operator such as flatMap or mergeAll.

Use flattening operators instead of nested subscriptions

***Note: RxJS imports have changed since the publication of this course. Operators now must be passed into `.pipe` to be applied to an observable.***

In this course we will learn to identify common mistakes with RxJS that usually make code harder to read and even introduce bugs. Most of these mistakes are related to Subject, subscribe, and subscriptions. We are going to see how to use only Observables and convenient operators made for solving those mistakes, such as fromEvent, takeUntil and switchMap. By the end of this course, you will have a more immediate intuition on what patterns are simple and safe in RxJS.

Save time avoiding common mistakes using RxJS

This lesson will show when to apply groupBy in the real world. This RxJS operator is best suited when a source observable represents many data sources, e.g. an observable for multitouch events. 

Use groupBy in Real RxJS Applications

Mapping the values of an observable to many inner observables is not the only way to create a higher order observable. RxJS also has operators that take a first order observable and return a higher order Observable. 

In this lesson we will learn about window, an operator to split an observable.

Split an RxJS Observable with Window

RxJS operators mergeMap and switchMap are useful for handling asynchronous responses from the server, but they can do much more. 

In this lesson, we will see how to use mergeMap to achieve the same functionality as map() or filter() or other custom behaviors. 

Use RxJS mergeMap for Fine-grain Custom Behavior

There are variants of the window operator that allow you to split RxJS observables in different ways. In this lesson we will explore the windowToggle variant and see one of its use cases in user interfaces. 

Split an RxJS Observable Conditionally with windowToggle

In this lesson we look at the common strategies for creating and flattening higher order observables in RxJS. In particular, we give switchMap a careful review. It is an operator that works as an "asyncMap" and is capable of solving many of our asynchronous problems in JavaScript.

Use switchMap as a Safe Default to Flatten Observables in RxJS

groupBy() is another RxJS operator to create higher order observables. In this lesson we will learn how groupBy works for routing source values into different groups according to a calculated key.

Split an RxJS Observable into Groups with groupBy

In this lesson, we will learn about switchMap, a shortcut for mapping to a higher order RxJS Observable, then flattening with switch. 

We will also see a practical example with network requests that would be used in the real world.

Use RxJS switchMap to Map and Flatten Higher Order Observables

An Observable may emit values of any JavaScript type: numbers, strings, booleans, objects, etc. This means an RxJS Observable may also happen to emit values which are themselves observables too. 

In this lesson we will learn more about this use case and begin learning about the so-called "higher order observables".

Get Started with Higher Order Observables in RxJS


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.


Create AI Prompts Based on a Directory of Files


With Cursor's "Composer" feature, you can select and entire directory and make changes to every file. This video walks through the process of selecting a folder and refactoring all the files from JavaScript to TypeScript. It also demonstrates other tips around generating terminal commands and customizing your main Cursor "Rules for AI".


Run an AI Refactor on Every File in a Directory with Cursor


This lesson breaks down the concept of asynchronous iterators and generators in JavaScript. Using the Node.js glob function as a practical example, you'll learn how Array.fromAsync facilitates the creation of arrays from asynchronous iterables and how generators can improve performance in file processing tasks.

Efficient File Processing in Node.js with Async Generators and Array.fromAsync

Learn the concept of asynchronous iterators and generators in JavaScript and Node.js Array.fromAsync


With the introduction of Svelte 5, the Svelte team has created a CLI, `sv`, that unifies all the tasks that previously spread across a handful of CLIS (create, add plugins, and migrate).

This lesson will create a Svelte project using the new `sv` CLI and build a counter component to showcase the new `$state`, `$derived`, and `$effect` runes that ship with the new version.



Get Started with Svelte 5 using the sv CLI

You'll create a SvelteKit project using the sv CLI and build a counter component showcasing Svelte $state, $derived, and $effect runes.



pnpm ships with a streamlined, easy way of managing Node.js versions for youself and your team. This video demonstrates why pnpm uses a specific version of Node.js, how to configure it globally, and how to set up your project so that anyone who is running your project will automatically use the same version of Node.js even if that version of Node.js is not installed.


use pnpm as a Node.js version manager

How you build with Angular has changed quite a lot over the years.

For example, the `inject` function was introduced in version 14 but you might still be familiar with Angular's constructor injection.

Similarly, structural directives like `ngif` or `ngfor` have been replaced with `@if` and `@for` blocks since version 17 and beyond.

These are patterns that need to be adjusted if you want to stay up-to-date with the latest Angular has to provide.

Luckily, Angular gives you great tools in the form of a migration CLI for supporting your migration efforts as you incrementally update your App from older version features and patterns. 

When you're done with this course you'll know how to target specific features, folders, and files to migrate to the latest Angular version.

You'll learn how to 'migrate':
- Structural directives with control flow syntax
- Constructor dependency inject to inject function
- Make components standalone
- Lazy load routes
- Input/Output decorators to signal-based API


Angular Migrations in Practice

Migrate old Angular patterns for version 18 and beyond

When we import assets in React components outside of the `public` folder that Nitro reads for assets by default when running the development server we need to tell Nitro how to find them with the `devProxy` configuration option.

```typescript
export default defineNitroConfig({
  renderer: './renderer.ts',
  devProxy: {
    '/app/assets': 'http://localhost:5173/app/assets'
  }
})
```

This is ultimately inadequate in scenarios where you want to import assets arbitrarily and have them "just work" but works in a pinch.



Use devProxy in Nitro Config to Serve Static Imported Assets in Dev Mode via Vite

Learn how to use devProxy in Nitro Config with Vite to serve static assets in React components in dev mode.

Start with a basic Vite React TypeScript app and enhance it for production use by integrating Nitro as the server. 

This requires a custom Vite plugin for nitro as well as a custom renderer and manually creating Nitro config.

The other way to approach this would be to add Vite to a Nitro app instead. Same basic result.

The [Nitro config reference](https://nitro.unjs.io/config) is a great read of you'd like to explore more options.


Configure a Vite React TypeScript Application on a Basic Nitro Server

Configure a Vite React TypeScript app by integrating Nitro for production, using custom plugins, renderers, and configs.

Quick Get Started style introduction to Vite using `pnpm create vite` with the React TypeScript template.

See [more in the official docs](https://vite.dev/guide/).

Create a Vite App with the React TypeScript Preset

Quick guide to start a Vite app using React TypeScript template with pnpm.

Over the years, your application have grown huge. Sometimes, really HUGE.

Many developers have contributed to the codebase. One day they pushed one coding style, a different one another day. Sometimes even different patterns and solutions for similar problems.

You want to keep your codebase consistent. In the Angular ecosystem, there were well established patterns for doing things the right way ™️. But the old solutions are being challenged by signal-based approach.

Eventually, you ask yourself the key question: **Should you integrate with the NEW solutions or stick to the battle-tested ones, but already considered LEGACY**?

That's a very good question indeed. Don't rush with architectural decisions 🤓.

## First, think of what problems you want to solve by introducing the change.

Do you have 1k LoC Angular components? Maybe even 2k? Do you and your team enjoy working with these? 😏

Where does the **domain logic and state management code** belong to - do you have a clear guidance on which code should be put where? Have you spot that different devs implement similar features in totally different ways?

Do you keep on asking the same questions over and over again: **whether this certain piece of code** should be **imperative** (plain old object properties and variables) or **reactive** (streams)? It'd be nice to keep all thinga reactive, but more often than not, it introduces complexity.

## Second, think of long-term consequences.

You are going to have more than one way to **manage the state**. But is that really an issue? If your codebase is modular, separate modules should not depend on each other in any way. Inner abstractions of one should be invisible to the other, etc.

You are going to introduce a **new tool**. On one hand, you need to learn it, and so does your team. But on the other hand, it's a breathe of fresh air. And it's useful to question the way you've been doing things so far. Maybe there's a more effective way?

You are going to embrace signal-based APIs. And that means taking taking advantage of Zoneless Angular. This means using all modern Angular APIs. And you know that signals are the future. Why would you want to stick to the **less performant, less type-safe, less flexible and, objectively, less effective solutions**?

## Finally, plan your INCREMENTAL integration.

INCREMENTAL is the absolute keyword here. You don't want to tell your PM you need to stop delivering features because of a refactor.

Actually, there's no need for a "refactor". Just pick the first new feature to be implemented. Or pick the one that needs to be extended.

NGRX Signal Store allows you to create both very simple & small stores, as well as bigger ones. **Composition** is the key here.

**Start simple**.

Create a `withState` section with the signals that hold the state. That's already reactive. And relatively simple.

```ts
const initialState: CartState = {
  items: ...,
  rebate: ...,
}

export const CartStore = signalStore(
  withState(initialState)
);
```

Create a `withMethods` section to provide ways to change the state:

```ts
export const CartStore = signalStore(
  ...
  withMethods((store) => ({
    addItem(item: ShoppingItem): void {
      patchState(store, (state) => ({ items: [ ...state.items, item ] }));
    },
    ...
);
```

Create a `withComputed` section to provide all derived computations:

```ts
export const CartStore = signalStore(
  ...
  withComputed(({ items }) => ({
    totalPrice: computed(() => items().reduce(...))
    ...
);
```

**Start simple**.

Now you can (literally) **`inject` this code into your existing solution**. All you need is to inject your brand new NGRX Signal Store implementation into a component, or a service:

```ts
@Injectable()
class ExistingBigService {
  cartStore = inject(CartStore)
  //...  
}
```

and that's it! What's beatiful is that NGRX Signal Store should remain an implementation details (of a component, service, etc). It **shouldn't leak outside to the entire application unintentionally**. Small NGRX Signal Stores help us to **keep logic more modular**.

Don't hesitate - give NGRX Signal Store a try! Start with the [_**Scalable Signals Angular Architecture with NGRX Signal Store**_](https://egghead.io/courses/scalable-signals-angular-architecture-with-ngrx-signal-store-a33abd39) course now!

Integrating NGRX Signal Store with an existing Angular application

Integrate NGRX Signal Store into your Angular app incrementally for modular, reactive state management. Improve consistency and performance with modern APIs.

André Staltz

Search Results