Why is there a need for another framework? the current approach is not producing fast sites, and this problem will not disappear by waiting for a faster CPU.

Foreword

Qwik in Action

Introduction to the frontend development. Now, the responsibility of creating good or bad applications depends on you because the means available are all there.

Introduction

Overview of TypeScript. TypeScript introduced types into an untyped language like Javascript to ensure code consistency.

TypeScript

Overview of the frontend architectures. In this lesson you will understand the difference from Client Side Rendering and Multi Page Application.

Frontend architectures

Overview of the hydration. In this lesson you will understand the difference from Hydration and Island architecture/Partial Hydration.

Hydration

React Server Component. In this lesson you will understand the difference from Server Component and Client Component.

React Server Component

Qwik resumability will change the frontend ecosystem, In this lesson you will understand why is so great.

Resumability, the Qwik way

Wrap up of frontend architectures module.

Summary Chapter 2

In this lesson you will be able to understand more about performance and you will understand how improve your application with less JavaScript.

Qwik, the framework built on top of closure-extraction

Resumability is the core concept behind Qwik. In this lesson you will understand better the process.

Resumability

Code Extraction is a topic hard to master, you will understand how it works with different approaches.

Code Extraction

JSX syntax is the most famous one because of React, but what about the other frameworks, Vue, Angular?

Why Qwik use JSX syntax

Summary Chapter 3

Let's see together the fundamentals of Qwik. In this lesson you will compare Webpack and Vite.

Getting started with Qwik

The Qwik build process is so important because the resumability process requires correct and intelligent bundling.

Qwik compilation Process

Qwik CLI and amazing tool to have a great Developer Experience with Qwik.

Technical requirements to start a new Qwik application

Qwik Middleware an easy and clever way to expose your RESTful APIs or GraphQL APIs.

Middleware

Wrap up of Getting Started with Qwik module.

Summary Chapter 4

In this lesson you will learn the pillars of SEO. You will lean few new terms and metrics that can help you to measure your application.

In this lesson you will learn the some new things about SEO and crawler.

Sitemap and robots files

Partytown an amazing library to execute third scripts in the service worker.

Partytown

Core Web Vitals are so important for own application. You will learn in detail all the metrics.

Core Web Vitals

Core Web Vitals Labs Data vs Field Data. These two information are so different, let's figure out the peculiarity of those.

Labs data vs Field data

Summary Chapter 5

SEO and Core Web Vitals

There are many ways to deploy a Qwik application. You can have your own server and deploy your Qwik application easily with the Qwik CLI and integrations.

Deploy Qwik in production

Cloud solution are a good alternative for a low cost pipeline and host. Nowadays these kind of services are so smart and great, you should try them.

Cloud solutions

With different team and many developers, it's important to master branching strategies to avoid problems during your day by day.

Branching strategies

Progressive Web App approach can be an alternative to the stores. You can publish you application with a lot of benefit with PWA.

Progressive Web App

Wrap up of Deploy Qwik in Production module.

Summary Chapter 6

Style an application is so important let's see how engage your Stakeholders into this process.

Style and render data with Qwik

CSS is so huge, there are a lot of ways to style your application with Qwik, let's see them together.

CSS and Built-In Styling Methods

Tailwind is an amazing library, let's see together how master it. I will share you some tips and tricks to use Tailwind in a better way.

Tailwind CSS

In this lesson you will learn how manage data with Qwik. There are a lot of APIs to explore, let's jump into the code.

Managing data with Qwik

Summary Chapter 7

In this lesson you will learn how architect a modern frontend end application.

Creating an e-commerce with Qwik and Supabase

In this lesson you will learn the trade offs of technical decisions. I share with you some tips and tricks.

Technological spike

In this lesson you will explore Supabase. This is an amazing service to leverage your business.

Supabase for your backend

A custom authentication is too complex and risky to implement from scratch. Let's use the Supabase auth to optimize our goals.

Let's talk about the Authentication process

Summary Chapter 8

Supabase CLI an handy tool to improve consistency across environments.

Supabase CLI

Let's use the Supabase CLI to manage our database migrations and schemas.

Supabase db migrations

In this lesson you will create the e-commerce homepage with the Supabase client to read the data.

Show products on our homepage

Every e-commerce has a detail page, let's create our product detail page with Qwik.

Product Detail

Cache is really useful and in this lesson I will explain in the detail how it works. I will share my experience in this topic with some cool analogies.

Cache-control headers

Summary Chapter 9

Rendering products with Orama full text search

Let's improve out application with a useful "Add to favorites" feature.

Add a product to your favorites list

In this lesson you will learn how to use Stripe to manage your payments in a secure way.

Adding cart and checkout process with Stripe

Let's try the Supabase database function. This is an easy way to allows us to do several things and also add some logic to our procedure.

Page views tracking

A real-time database with Supabase is so simple to implement, let's build together a new functionality with this great feature.

Real-time database

Summary Chapter 10

Let's explore together the benefit of testing. In this lesson you will explore the various types of tests, Unit Test, E2E, Visual regression tests and more.

Overview of application testing

Let's discuss together how and when testing is valuable for our business. 3X Explore/Expand/Extract can help us is this reasoning.

How much testing is enough? When do I write tests?

In this lesson you will lean the Test driven development TDD flow. It's a really good practice to put in place.

Test-Driven Development (TDD)

In this lesson you will lean how test your components with Cypress.

Let's add some tests with Cypress

Do you need a Qwik component library? Qwik UI is the project for you because can give you a lot of Qwik accessible components out of the box.

Qwik UI

Summary Chapter 11

Adding tests to our Qwik application

Let's explore a bit of history of Qwik. A new framework with a great past.

Final thoughts

Qwik and React together, no problem, qwikify$ is the API to solve your problems.

qwikify$

Qwik and Astro together, no problem, @qwikdev/astro is the library to solve your problems.

Qwik inside Astro application

Qwik and micro-frontends together, no problem, out of the box Qwik can manage this scenario with no external dependencies.

Micro-frontends with Qwik

Summary chapter 12

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( the primaryDescriptionMarkdown is long - several lines, include images, as long as you want )

In this course we <headline of what we do>. <why this technology is good> but <here's how learning it is problem>. 

In <the length of these lessons> we cover <three salient points about what we cover. Your BEST points>. Its <however long it is> and comes with <these bonus features, and reasons to buy. code, etc.>

It's taught by <author name> who <credibility, reason you should listen to them>. <social proof, if you have it yet>

<then you can list other supporting stuff you want to add, anything you want here>

-------
Example:
-------

We created a free course to create your first GraphQL server (from scratch) using Node and TypeScript. TypeScript and GraphQL are a powerful combo, but there's a lot of confusing edges if you're getting it setup the first time.

In this course we cover the basics of getting TypeScript setup with Node, how GraphQL works, and how to set up a GraphQL server using Apollo server. It's two hours long, it comes with complete code examples, and we walk through the code step-by-step.

It's taught by my friend, Shopify-engineer Hassan Djirdeh and he's integrated what he's learned using GraphQL in production as an engineer at Shopify. We've already had over 1,300 students enroll and it's been getting great reviews so far.

// ... and so on

Harness Qwik Resumable Architecture for Lightning-Fast Startup Times

In this course we <headline of what we do>. <why this technology is good> but <here's how learning it is problem>. 

( the summary is short - one or two lines )

Complete Guide to Qwik

Now that the basics of making applications visually appealing have been covered, the focus can shift to understanding how to read data from external sources. This capability enhances the applications, making them more engaging and providing the user with the most enjoyable experience possible. Consider this example: during a login procedure, interaction with the application changes its state. The application "remembers" the user and allows access to personal information. Specifically, in Qwik, there are several ways to manage the state of the application, but the fundamental idea is to simplify the developer's work. In this chapter, different approaches to managing application states will be explored and reviewed with some examples.

The low-level Qwik API that will be most beneficial in managing an app's application state is 

. It takes an initial value and returns a reactive signal. This reactive signal is an object with a single property 

. Changing this property will automatically update any component that depends on it.

export default component$(() => {
  const countSig = useSignal(123);

  return (
    <div>
      Count: {countSig.value}
      <button onClick$={() => countSig.value++}>
        Increment
      </button>
    </div>
  );
});

A naming convention has been defined to use the 

 suffix for signals variable names to make the component code more "Scannable".

, a reactive variable with an initial value of 123 is established. As soon as it's modified (through the 

 event), it triggers an update to the UI. Signals are highly efficient because the framework can track where that signal is read, allowing it to update things accordingly with a precise change without having to check and re-render the DOM of the components.

The signal mentioned earlier has an initial value of 123. In previous chapters, it was learned that during the build phase, the Qwik Optimizer packages the application to send it to the browser in anticipation of external events. With external events, the bundles necessary to make the application interactive will be executed. But if the application state needs to be changed and the initial value is 123, where can this information be obtained from? After all, on the first click, the value will have to increase by 1 and, therefore, go to 124. The answer is simple. In the static HTML that the server sends to the browser, the Qwik Optimizer also has the task of serializing the application state. It inserts it directly into the HTML page, and if the HTML sent by the browser is inspected, there is a 

 script, which contains the initial value, 123.

This value will then be retrieved and injected into the JavaScript, which is necessary to make the counter interactive. By doing so, not only can the JavaScript be executed when necessary, but also the application state can be recovered and resumed from the point where the server had serialized the application.

In the previous example, something simple was done, but how can more complex states be managed? The 

 as it accepts an initial value and, by default, reactively tracks the properties that are nested in it, returning a reactive object. Essentially, it's about many signals that together make up a more complex object, ensuring its reactivity.

export default component$(() => {
  const state = useStore({ count: 0 });

  return (
    <>
      <button onClick$={() => state.count++}>
        Increment
      </button>
      <p>Count: {state.count}</p>
    </>
  );
});

This example is very similar to the previous one. 

 is still used, but this time the store is being updated.

 need to be allocated. This can be a performance issue if you have many nested properties; in that case, you can use the 

 option to track only top-level properties. When we create a store, by default, the deep option is false.

In the previous examples, how to declare a local state was discussed. However, with 

, a global state in the application can be declared. The alternative to a global state would be to pass the information, component by component, within the props of each one, generating the so-called 

. To avoid this, it's good practice to create a global state.

---
title: Managing data with Qwik
description: In this lesson you will learn how manage data with Qwik. There are a lot of APIs to explore, let's jump into the code.
---

# Managing Data with Qwik

Now that the basics of making applications visually appealing have been covered, the focus can shift to understanding how to read data from external sources. This capability enhances the applications, making them more engaging and providing the user with the most enjoyable experience possible. Consider this example: during a login procedure, interaction with the application changes its state. The application "remembers" the user and allows access to personal information. Specifically, in Qwik, there are several ways to manage the state of the application, but the fundamental idea is to simplify the developer's work. In this chapter, different approaches to managing application states will be explored and reviewed with some examples.

## Local State Management

### useSignal

The low-level Qwik API that will be most beneficial in managing an app's application state is `useSignal`. It takes an initial value and returns a reactive signal. This reactive signal is an object with a single property `.value`. Changing this property will automatically update any component that depends on it.

Consider this example:

```typescript
export default component$(() => {
  const countSig = useSignal(123);

  return (
    <div>
      Count: {countSig.value}
      <button onClick$={() => countSig.value++}>
        Increment
      </button>
    </div>
  );
});
```

> A naming convention has been defined to use the `Sig` suffix for signals variable names to make the component code more "Scannable".

In this example created via `useSignal`, a reactive variable with an initial value of 123 is established. As soon as it's modified (through the `onClick$` event), it triggers an update to the UI. Signals are highly efficient because the framework can track where that signal is read, allowing it to update things accordingly with a precise change without having to check and re-render the DOM of the components.

### Qwik Optimizer

The signal mentioned earlier has an initial value of 123. In previous chapters, it was learned that during the build phase, the Qwik Optimizer packages the application to send it to the browser in anticipation of external events. With external events, the bundles necessary to make the application interactive will be executed. But if the application state needs to be changed and the initial value is 123, where can this information be obtained from? After all, on the first click, the value will have to increase by 1 and, therefore, go to 124. The answer is simple. In the static HTML that the server sends to the browser, the Qwik Optimizer also has the task of serializing the application state. It inserts it directly into the HTML page, and if the HTML sent by the browser is inspected, there is a `type="qwik/json"` script, which contains the initial value, 123.

![qwik-json](https://d2uusema5elisf.cloudfront.net/courses/complete-guide-to-qwik/module_07/lesson_07.04/public/assets/qwik-json.png)

This value will then be retrieved and injected into the JavaScript, which is necessary to make the counter interactive. By doing so, not only can the JavaScript be executed when necessary, but also the application state can be recovered and resumed from the point where the server had serialized the application.

### useStore

In the previous example, something simple was done, but how can more complex states be managed? The `useStore` API can be used. It's very similar to `useSignal,` as it accepts an initial value and, by default, reactively tracks the properties that are nested in it, returning a reactive object. Essentially, it's about many signals that together make up a more complex object, ensuring its reactivity.

Consider this example:

```typescript
export default component$(() => {
  const state = useStore({ count: 0 });

  return (
    <>
      <button onClick$={() => state.count++}>
        Increment
      </button>
      <p>Count: {state.count}</p>
    </>
  );
});
```

This example is very similar to the previous one. `onClick$` is still used, but this time the store is being updated.

> Note that for `useStore` to track all nested properties, many [Proxy objects](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy) need to be allocated. This can be a performance issue if you have many nested properties; in that case, you can use the `"deep: false"` option to track only top-level properties. When we create a store, by default, the deep option is false.

## Global State Management with useContext

In the previous examples, how to declare a local state was discussed. However, with `useContext`, a global state in the application can be declared. The alternative to a global state would be to pass the information, component by component, within the props of each one, generating the so-called `props drilling`. To avoid this, it's good practice to create a global state.

Consider this example:

```typescript
// 1
interface UsersStore {
  users: User[];
}
// 2
export const UsersContext =
  createContextId<UsersStore>("Users");

// 3
export const App = component$(() => {
  useContextProvider(
    UsersContext,
    useStore<UsersStore>({
      users: [{ firstName: "John", lastName: "Doe" }],
    })
  );

  return <ChildComponent />;
});

// 4
export const ChildComponent = component$(() => {
  const todos = useContext(UsersContext);
  return (
    <ul>
      {todos.items.map((item) => (
        <li>{item}</li>
      ))}
    </ul>
  );
});
```

This example introduces several new concepts, but let's break them down step by step.

-   **1**: The TypeScript type for the global state, which will be a list of users, is created.
-   **2**: An id with `createContextId` is created, which will allow the global state to be uniquely referenced.
-   **3**: In the App component with `useContextProvider,` the id ( `UsersContext` ), and the initial value, the global state can finally be created.
-   **4**: In the child component, `useContext(UsersContext)` can be used to retrieve the list of users from the global state.