Building with Qwik Framework

Qwik represents a paradigm shift in web development, offering unprecedented performance through its unique resumability approach. Let's explore how to build modern web applications using this innovative framework.

Understanding Qwik

Qwik's core principles include:

• Resumability over hydration
• Zero JavaScript by default
• Progressive loading
• Fine-grained lazy loading
• Server-side rendering

Basic Setup

Project Initialization

Create a new Qwik project:

npm create qwik@latest
cd my-qwik-app
npm install
npm start

Component Structure

Create your first component:

import { component$ } from '@builder.io/qwik';

export const Greeting = component$(() => {
    return (
        <div>
            <h1>Hello, Qwik!</h1>
        </div>
    );
});

Core Concepts

Reactive State

Implement reactive state management:

import { component$, useSignal } from '@builder.io/qwik';

export const Counter = component$(() => {
    const count = useSignal(0);

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

Resource Loading

Handle data fetching:

import { component$, Resource, useResource$ } from '@builder.io/qwik';

export const UserProfile = component$(() => {
    const userResource = useResource$(async () => {
        const response = await fetch('/api/user');
        return response.json();
    });

    return (
        <Resource
            value={userResource}
            onPending={() => <div>Loading...</div>}
            onRejected={(error) => <div>Error: {error.message}</div>}
            onResolved={(user) => (
                <div>
                    <h2>{user.name}</h2>
                    <p>{user.email}</p>
                </div>
            )}
        />
    );
});

Advanced Features

Lazy Loading

Implement lazy loading:

import { component$, useTask$ } from '@builder.io/qwik';

export const LazyComponent = component$(() => {
    useTask$(async () => {
        const module = await import('./heavy-module');
        // Use module
    });

    return <div>Lazy loaded content</div>;
});

Form Handling

Create form components:

import { component$, useSignal, $ } from '@builder.io/qwik';

export const ContactForm = component$(() => {
    const formState = useSignal({
        name: '',
        email: '',
        message: ''
    });

    const handleSubmit = $((event: Event) => {
        event.preventDefault();
        // Handle form submission
        console.log(formState.value);
    });

    return (
        <form onSubmit$={handleSubmit}>
            <input
                type="text"
                onInput$={(e) => formState.value.name = e.target.value}
                value={formState.value.name}
            />
            <button type="submit">Submit</button>
        </form>
    );
});

Real-World Applications

Authentication System

Implement user authentication:

import { component$, useStore } from '@builder.io/qwik';

export const Auth = component$(() => {
    const auth = useStore({
        isAuthenticated: false,
        user: null
    });

    const login = $(async (credentials) => {
        const response = await fetch('/api/login', {
            method: 'POST',
            body: JSON.stringify(credentials)
        });

        const data = await response.json();
        auth.isAuthenticated = true;
        auth.user = data.user;
    });

    return (
        <div>
            {auth.isAuthenticated ? (
                <UserDashboard user={auth.user} />
            ) : (
                <LoginForm onSubmit$={login} />
            )}
        </div>
    );
});

Data Grid

Create a data grid component:

import { component$, useSignal, useTask$ } from '@builder.io/qwik';

export const DataGrid = component$(() => {
    const data = useSignal([]);
    const sorting = useSignal({ field: 'id', direction: 'asc' });

    useTask$(async ({ track }) => {
        track(() => sorting.value);

        const response = await fetch(
            `/api/data?sort=${sorting.value.field}&dir=${sorting.value.direction}`
        );
        data.value = await response.json();
    });

    return (
        <table>
            <thead>
                <tr>
                    <th onClick$={() => updateSort('id')}>ID</th>
                    <th onClick$={() => updateSort('name')}>Name</th>
                </tr>
            </thead>
            <tbody>
                {data.value.map((row) => (
                    <tr key={row.id}>
                        <td>{row.id}</td>
                        <td>{row.name}</td>
                    </tr>
                ))}
            </tbody>
        </table>
    );
});

Best Practices

Performance Optimization

Optimize component performance:

import { component$, useVisibleTask$ } from '@builder.io/qwik';

export const OptimizedComponent = component$(() => {
    useVisibleTask$(() => {
        // Only runs when component is visible
        performHeavyOperation();
    });

    return <div>Optimized content</div>;
});

State Management

Implement efficient state management:

import { createContextId, useContextProvider, useContext } from '@builder.io/qwik';

export const TodoContext = createContextId('TodoContext');

export const TodoProvider = component$(() => {
    const todos = useStore({
        items: [],
        filter: 'all'
    });

    useContextProvider(TodoContext, todos);

    return <Slot />;
});

Testing

Component Testing

Write component tests:

import { createDOM } from '@builder.io/qwik/testing';

describe('Counter', () => {
    it('should increment count', async () => {
        const { screen, userEvent } = await createDOM();
        await render(<Counter />);

        const button = screen.querySelector('button');
        await userEvent.click(button);

        expect(screen.querySelector('p').textContent)
            .toBe('Count: 1');
    });
});

Conclusion

Qwik offers a revolutionary approach to web development with:

• Optimal performance
• Easy state management
• Efficient resource loading
• Progressive enhancement
• Developer-friendly APIs

Key takeaways:

• Leverage resumability
• Use fine-grained reactivity
• Implement lazy loading
• Optimize for performance
• Follow best practices

Remember to:

• Start with server-side rendering
• Progressively enhance functionality
• Monitor performance metrics
• Test thoroughly
• Keep up with Qwik updates