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Welcome to the comprehensive guide for migrating from Aurelia 1 to Aurelia 2! This guide will walk you through every aspect of the migration process, highlighting what's changed, what's improved, and what you need to know to successfully upgrade your application.

Aurelia 2 represents a significant evolution of the framework, bringing modern JavaScript features, improved performance, better tooling support, and a more streamlined developer experience. While many core concepts remain familiar, there are important changes that will make your applications more maintainable and powerful.


Table of Contents


Application Bootstrapping

The HTML Entry Point

The way you initialize your Aurelia application has been simplified and modernized.

The aurelia-app attribute told the framework where to find your main configuration file, and you had to include the aurelia-bootstrapper script.

Much cleaner! You simply place your root component's element in the HTML. No special attributes or bootstrap scripts needed. Your bundler configuration determines which JavaScript file serves as the entry point.

Application Configuration and Startup

The main configuration file has been significantly streamlined, with a more intuitive API and better bundler compatibility.

Key concepts in v1:

  • PLATFORM.moduleName: Required for Webpack compatibility - you had to wrap every module reference

  • standardConfiguration(): Loaded default framework features

Registering Global Resources

Making components available throughout your app is now more flexible and type-safe.


Components and Templates

Component Structure

Components in Aurelia 2 maintain the same view-model pairing but with enhanced conventions and flexibility.

Key improvements:

  • <import> vs <require>: More intuitive import syntax

  • Auto-CSS loading: CSS files with matching names are loaded automatically

Template Syntax Enhancements

Aurelia 2 maintains familiar binding syntax while adding powerful new features.

New features in v2:

  • Lambda expressions: Filter and transform data directly in templates


Component Lifecycle

The component lifecycle has been expanded and refined with more hooks and better async support.

V1 Lifecycle Order: constructor → created → bind → attached → detached → unbind

V2 Lifecycle Order: constructor → define → hydrating → hydrated → created → binding → bound → attaching → attached → detaching → unbinding → dispose

Key improvements:

  • More granular control: Additional hooks for different stages

  • Better async support: Return Promises to control timing


Dependency Injection

Aurelia 2's DI system has been significantly enhanced with better type safety and more flexible registration options.

Key improvements:

  • resolve() function: Clean property injection without constructor bloat

  • Better type safety: Full TypeScript support with interfaces


Logging System

The logging system has been completely redesigned with a more powerful and flexible architecture.

Key improvements:

  • Sink-based architecture: More flexible than appenders

  • Better type safety: Full TypeScript support

  • Dependency injection: Seamless integration with DI system


Router and Navigation

The router has been redesigned with a focus on type safety, better performance, and modern navigation patterns.

Key improvements:

  • Declarative routing: Routes defined with decorators and configuration objects

  • Better lifecycle hooks: canLoad/loading vs canActivate/activate, canUnload/unloading vs canDeactivate/deactivate


Data Binding

Data binding has been enhanced with better performance, new features, and more intuitive syntax.

Key improvements:

  • .class binding: Clean conditional CSS classes

  • Automatic computation: No need for @computedFrom decorator


What's New in Aurelia 2

Beyond the improvements to existing features, Aurelia 2 introduces several entirely new capabilities:

Shadow DOM Support

Custom Attribute Patterns

Create your own binding syntax!

Enhanced Custom Elements

Watch Decorator for Advanced Observation


Migration Checklist

Use this checklist to ensure you've covered all aspects of your migration:

🏗️ Project Setup

🧩 Components

🔗 Data Binding

🚦 Routing

💉 Dependency Injection

📝 Logging

🎨 Templates and Features

🧪 Testing

🔧 Advanced Features


Conclusion

Migrating from Aurelia 1 to Aurelia 2 brings significant benefits: better performance, improved developer experience, enhanced type safety, and modern JavaScript features. While there are changes to learn, the core concepts remain familiar, and the improvements make building applications more enjoyable and maintainable.

The enhanced DI system, redesigned router, automatic observation, and new template features make Aurelia 2 a powerful platform for building modern web applications. Take your time with the migration, test thoroughly, and don't hesitate to leverage the new features that make development more productive.

Remember that Aurelia 2 maintains the same philosophy of convention over configuration and stays out of your way, while providing powerful tools when you need them. The migration effort will be rewarded with a more maintainable, performant, and developer-friendly application.

globalResources()
: Made components available app-wide
  • feature(): Loaded grouped functionality

  • plugin(): Added third-party packages

  • setRoot(): Defined the root component

  • What's improved in v2:

    • No more PLATFORM.moduleName: Works with any bundler out of the box

    • Fluent API: Chain registration and startup calls naturally

    • Type safety: Full TypeScript support with IntelliSense

    • Flexible registration: Multiple ways to register components and features

    • Better async support: Native Promise support throughout

    resolve() function: Alternative to constructor injection for better composability

  • No <template> wrapper: Optional in v2 for cleaner templates

  • Modern CSS support: Full compatibility with modern CSS features

  • Enhanced parameters: Controllers provide more context

  • Proper cleanup: dispose hook for final cleanup

  • DI.createInterface()
    : Create typed injection tokens with defaults
  • Flexible registration: Multiple patterns for different needs

  • Enhanced resolvers: More powerful dependency resolution strategies

  • Scoped loggers: Easy categorization and filtering

  • Multiple outputs: Send logs to different destinations simultaneously

  • Type safety: Full TypeScript support throughout

  • Lazy loading: Built-in support for code splitting

  • Enhanced parameters: Better access to route context and navigation state

  • Dynamic titles: Easy to set page titles based on loaded data

  • Lambda expressions: Filter and transform data in templates
  • Better ref binding: component.ref for accessing component instances

  • Function return in events: Event handlers can return functions

  • to
    <au-viewport>
  • Verify event binding and handling
    Application Bootstrapping
    Components and Templates
    Component Lifecycle
    Dependency Injection
    Logging System
    Router and Navigation
    Data Binding
    Template Features
    What's New in Aurelia 2
    Migration Checklist
    // src/main.ts
    import Aurelia, { RouterConfiguration, LoggerConfiguration, LogLevel } from 'aurelia';
    import { MyApp } from './my-app';
    
    // Quick startup (recommended for most apps)
    Aurelia
      .register(RouterConfiguration)
      .app(MyApp)
      .start();
    
    // Or with more configuration
    Aurelia
      .register(
        RouterConfiguration.customize({ useUrlFragmentHash: false }),
        LoggerConfiguration.create({
          level: LogLevel.debug,
          sinks: [ConsoleSink]
        })
      )
      .app(MyApp)
      .start();
    
    // Or verbose startup for advanced scenarios
    const au = new Aurelia();
    au.register(
      RouterConfiguration,
      // Register global components
      NavBarComponent,
      FooterComponent
    );
    au.app({
      host: document.querySelector('my-app'),
      component: MyApp
    });
    await au.start();
    <!-- index.html -->
    <!DOCTYPE html>
    <html>
      <head>
        <meta charset="utf-8">
        <title>My Aurelia App</title>
      </head>
      <body aurelia-app="main">
        <script src="scripts/vendor-bundle.js" data-main="aurelia-bootstrapper"></script>
      </body>
    </html>
    <!-- index.html -->
    <!DOCTYPE html>
    <html>
      <head>
        <meta charset="utf-8">
        <title>My Aurelia App</title>
        <meta name="viewport" content="width=device-width, initial-scale=1">
      </head>
      <body>
        <my-app></my-app>
      </body>
    </html>
    // src/main.ts
    export function configure(aurelia: Aurelia): void {
      aurelia.use
        .standardConfiguration()
        .feature(PLATFORM.moduleName('resources/index'))
        .globalResources(PLATFORM.moduleName('./shared/nav-bar'));
    
      aurelia.use.developmentLogging(environment.debug ? 'debug' : 'warn');
    
      if (environment.testing) {
        aurelia.use.plugin(PLATFORM.moduleName('aurelia-testing'));
      }
    
      aurelia.start()
        .then(() => aurelia.setRoot(PLATFORM.moduleName('app')));
    }
    // Individual registration
    aurelia.use.globalResources(
      PLATFORM.moduleName('shared/value-converters/date-format'),
      PLATFORM.moduleName('shared/components/loading-spinner')
    );
    
    // Feature-based registration
    // resources/index.ts
    export function configure(config: FrameworkConfiguration) {
      config.globalResources([
        PLATFORM.moduleName('./value-converters/date-format'),
        PLATFORM.moduleName('./components/loading-spinner')
      ]);
    }
    // Method 1: Direct registration
    Aurelia
      .register(
        DateFormatValueConverter,
        LoadingSpinnerComponent,
        RouterConfiguration
      )
      .app(MyApp)
      .start();
    
    // Method 2: Registry pattern (recommended)
    // shared/registry.ts
    export * from './value-converters/date-format';
    export * from './components/loading-spinner';
    export * from './custom-attributes/tooltip';
    
    // main.ts
    import * as SharedResources from './shared/registry';
    
    Aurelia
      .register(SharedResources)
      .app(MyApp)
      .start();
    
    // Method 3: Plugin-style with configuration
    // shared/shared-plugin.ts
    export const SharedPlugin = {
      register(container: IContainer) {
        container.register(
          DateFormatValueConverter,
          LoadingSpinnerComponent,
          TooltipCustomAttribute
        );
      },
      customize(callback: (options: SharedOptions) => void) {
        // Custom configuration logic
        return this;
      }
    };
    <!-- src/app.html -->
    <require from="./shared/nav-bar"></require>
    <require from="./styles.css"></require>
    
    <template>
      <nav-bar router.bind="router"></nav-bar>
      <div class="content">
        <h1>${message}</h1>
        <router-view></router-view>
      </div>
    </template>
    // src/app.ts
    import { autoinject } from 'aurelia-framework';
    import { Router } from 'aurelia-router';
    
    @autoinject
    export class App {
      public message: string;
    
      constructor(private router: Router) {
        this.message = 'Welcome to Aurelia!';
      }
    }
    /* src/app.css - had to be manually required */
    .content {
      padding: 20px;
    }
    <!-- src/my-app.html -->
    <import from="./shared/nav-bar"></import>
    
    <nav-bar router.bind="router"></nav-bar>
    <div class="content">
      <h1>${message}</h1>
      <au-viewport></au-viewport>
    </div>
    // src/my-app.ts
    import { IRouter } from '@aurelia/router';
    import { resolve } from '@aurelia/kernel';
    
    export class MyApp {
      public message = 'Welcome to Aurelia 2!';
      private router: IRouter = resolve(IRouter);
    
      // Constructor injection still works
      // constructor(@IRouter private router: IRouter) {}
    }
    /* src/my-app.css - automatically loaded by convention! */
    .content {
      padding: 20px;
      container-type: inline-size; /* Modern CSS features work great */
    }
    <template>
      <!-- Basic binding -->
      <div class="user-card ${isActive ? 'active' : ''}">
        <img src.bind="user.avatar" alt="Avatar">
        <span>${user.name}</span>
      </div>
    
      <!-- Conditional rendering -->
      <div if.bind="showDetails">
        <p>${user.bio}</p>
      </div>
    
      <!-- Repeating -->
      <ul>
        <li repeat.for="item of items" class="${$index % 2 === 0 ? 'even' : 'odd'}">
          ${item.name}
        </li>
      </ul>
    </template>
    <!-- No <template> wrapper needed -->
    <div class="user-card" active.class="isActive">
      <img src.bind="user.avatar" alt="Avatar">
      <span>${user.name}</span>
    </div>
    
    <!-- CSS class binding made easy -->
    <button
      class="btn"
      primary.class="isPrimary"
      loading.class="isLoading"
      disabled.class="isDisabled">
      ${buttonText}
    </button>
    
    <!-- Lambda expressions in templates -->
    <ul>
      <li repeat.for="user of users.filter(u => u.isActive)">
        ${user.name}
      </li>
    </ul>
    export class UserProfile {
      private user: User;
    
      // Component lifecycle hooks
      constructor() {
        // Basic initialization only
      }
    
      created() {
        // Called after the component is created
        this.initializeDefaults();
      }
    
      bind() {
        // Called when binding begins
        this.loadUserData();
      }
    
      attached() {
        // Called when added to DOM
        this.setupEventListeners();
      }
    
      unbind() {
        // Called when unbinding
        this.cleanup();
      }
    
      detached() {
        // Called when removed from DOM
        this.removeEventListeners();
      }
    }
    import { ICustomElementController } from 'aurelia';
    
    export class UserProfile {
      private user: User;
    
      constructor() {
        // Basic initialization - same as v1
      }
    
      // NEW: Modify component definition before hydration
      define(controller: ICustomElementController, definition: CustomElementDefinition) {
        // Rare use case - modify component behavior dynamically
        return { ...definition, shadowOptions: { mode: 'open' } };
      }
    
      // NEW: Add contextual DI registrations
      hydrating(controller: ICustomElementController) {
        // Register services that child components might need
        controller.container.register(UserService.singleton());
      }
    
      // NEW: Final setup before child creation
      hydrated(controller: ICustomElementController) {
        // All child components are about to be created
      }
    
      created(controller: ICustomElementController) {
        // Same as v1 but with controller access
        this.initializeDefaults();
      }
    
      // Enhanced with async support and better parameters
      async binding(initiator: IHydratedController, parent: IHydratedController | null) {
        // Can return Promise to block child binding until resolved
        await this.loadUserData();
      }
    
      // NEW: Called after all bindings are set
      bound(initiator: IHydratedController, parent: IHydratedController | null) {
        // Values from let, from-view, and ref bindings are now available
        this.processBindingData();
      }
    
      // NEW: Called when attaching to DOM (before attached)
      async attaching(initiator: IHydratedController, parent: IHydratedController | null) {
        // Can return Promise for entrance animations
        return this.animateIn();
      }
    
      attached(initiator: IHydratedController) {
        // Same concept as v1 but only receives initiator parameter
        this.setupEventListeners();
      }
    
      // NEW: Called when detaching from DOM (before detached)
      async detaching(initiator: IHydratedController, parent: IHydratedController | null) {
        // Can return Promise for exit animations
        return this.animateOut();
      }
    
      unbinding(initiator: IHydratedController, parent: IHydratedController | null) {
        // Enhanced with better parameters
        this.cleanup();
      }
    
      // NEW: Final cleanup when component is permanently discarded
      dispose() {
        // One-time cleanup for memory leak prevention
        this.finalCleanup();
      }
    }
    import { autoinject, Container } from 'aurelia-framework';
    
    // Service registration
    const container = new Container();
    container.registerSingleton(UserService);
    container.registerTransient(ApiClient);
    container.registerInstance(IConfig, { apiUrl: '/api' });
    
    // Using services
    @autoinject
    export class UserManager {
      constructor(
        private userService: UserService,
        private apiClient: ApiClient
      ) {}
    }
    
    // Manual injection
    export class UserManager {
      static inject = [UserService, ApiClient];
    
      constructor(userService, apiClient) {
        this.userService = userService;
        this.apiClient = apiClient;
      }
    }
    
    // Resolvers
    import { Lazy, All, Optional, Parent, Factory, NewInstance } from 'aurelia-framework';
    
    @autoinject
    export class ComplexService {
      constructor(
        @Lazy(ExpensiveService) private expensiveServiceFactory: () => ExpensiveService,
        @All(IPlugin) private plugins: IPlugin[],
        @Optional(IOptionalService) private optionalService: IOptionalService
      ) {}
    }
    import { DI, Registration, resolve, inject, singleton, transient } from 'aurelia';
    
    // Service registration - more flexible and type-safe
    const container = DI.createContainer();
    container.register(
      Registration.singleton(UserService, UserService),
      Registration.transient(ApiClient, ApiClient),
      Registration.instance(IConfig, { apiUrl: '/api' })
    );
    
    // Using services - property injection with resolve() (recommended)
    export class UserManager {
      // Property injection with resolve() - clean and flexible
      private userService = resolve(UserService);
      private apiClient = resolve(ApiClient);
    
      // Note: Constructor injection also works, but resolve() is the recommended pattern
    }
    
    // Decorator-based registration
    @singleton()
    export class UserService {
      // Automatically registered as singleton
    }
    
    @transient()
    export class TemporaryService {
      // New instance every time
    }
    
    // Interface creation made easy
    export const IUserService = DI.createInterface<IUserService>(
      'IUserService',
      x => x.singleton(UserService) // Default implementation
    );
    export type IUserService = UserService;
    
    // Enhanced resolvers
    import { lazy, all, optional, factory, newInstanceOf, newInstanceForScope } from 'aurelia';
    
    export class ComplexService {
      // Property injection with resolvers
      private expensiveService = resolve(lazy(ExpensiveService));
      private plugins = resolve(all(IPlugin));
      private optionalService = resolve(optional(IOptionalService));
      private serviceFactory = resolve(factory(SomeService));
      private uniqueInstance = resolve(newInstanceOf(SomeService));
    
      useServices() {
        const expensive = this.expensiveService(); // Lazy evaluation
        this.plugins.forEach(plugin => plugin.execute());
      }
    }
    
    // Create injectable services with default implementations
    export const INotificationService = DI.createInterface<INotificationService>(
      'INotificationService',
      x => x.singleton(ToastNotificationService)
    );
    
    export interface INotificationService {
      notify(message: string): void;
      error(message: string): void;
    }
    // main.ts
    import * as LogManager from 'aurelia-logging';
    import { ConsoleAppender } from 'aurelia-logging-console';
    
    export function configure(aurelia) {
      LogManager.addAppender(new ConsoleAppender());
      LogManager.setLevel(LogManager.logLevel.debug);
    
      aurelia.start().then(() => aurelia.setRoot());
    }
    
    // Custom appender
    export class CustomAppender {
      debug(logger, ...rest) {
        console.debug(`DEBUG [${logger.id}]`, ...rest);
      }
    
      info(logger, ...rest) {
        console.info(`INFO [${logger.id}]`, ...rest);
      }
    
      warn(logger, ...rest) {
        console.warn(`WARN [${logger.id}]`, ...rest);
      }
    
      error(logger, ...rest) {
        console.error(`ERROR [${logger.id}]`, ...rest);
      }
    }
    
    // Using logger
    import { getLogger } from 'aurelia-logging';
    
    export class UserService {
      private logger = getLogger('UserService');
    
      loadUser(id: string) {
        this.logger.debug(`Loading user ${id}`);
      }
    }
    // main.ts - Simple setup
    import Aurelia, { LoggerConfiguration, LogLevel, ConsoleSink } from 'aurelia';
    
    Aurelia
      .register(LoggerConfiguration.create({
        level: LogLevel.debug,
        sinks: [ConsoleSink]
      }))
      .app(MyApp)
      .start();
    
    // Advanced setup with custom sinks
    import { sink, ISink, ILogEvent } from '@aurelia/kernel';
    
    @sink({ handles: [LogLevel.warn, LogLevel.error] })
    export class RemoteLogSink implements ISink {
      handleEvent(event: ILogEvent): void {
        // Send to remote logging service
        fetch('/api/logs', {
          method: 'POST',
          body: JSON.stringify({
            level: event.level,
            message: event.toString(),
            timestamp: new Date().toISOString()
          })
        });
      }
    }
    
    // Multiple sinks with different configurations
    Aurelia
      .register(LoggerConfiguration.create({
        level: LogLevel.trace,
        sinks: [ConsoleSink, RemoteLogSink, FileLogSink]
      }))
      .app(MyApp)
      .start();
    
    // Using logger - recommended property injection with resolve()
    import { resolve } from '@aurelia/kernel';
    import { ILogger } from '@aurelia/kernel';
    
    export class UserService {
      private logger = resolve(ILogger).scopeTo('UserService');
    
      async loadUser(id: string) {
        this.logger.debug(`Loading user ${id}`);
    
        try {
          const user = await this.api.getUser(id);
          this.logger.info(`User ${id} loaded successfully`);
          return user;
        } catch (error) {
          this.logger.error(`Failed to load user ${id}`, error);
          throw error;
        }
      }
    }
    // Router configuration
    export class App {
      router: Router;
    
      configureRouter(config: RouterConfiguration, router: Router) {
        config.title = 'My App';
        config.map([
          { route: ['', 'home'], name: 'home', moduleId: 'pages/home', nav: true, title: 'Home' },
          { route: 'users/:id', name: 'user', moduleId: 'pages/user-detail', title: 'User' },
          { route: 'admin/*path', name: 'admin', moduleId: 'areas/admin/index', title: 'Admin' }
        ]);
    
        this.router = router;
      }
    }
    
    // Lifecycle hooks
    export class UserDetail {
      user: User;
    
      canActivate(params: any, routeConfig: RouteConfig, navigationInstruction: NavigationInstruction) {
        // Check if user can access this route
        if (!this.authService.isAuthenticated()) {
          return new Redirect('login');
        }
        return true;
      }
    
      activate(params: any, routeConfig: RouteConfig, navigationInstruction: NavigationInstruction) {
        // Load data for the route
        return this.userService.getUser(params.id).then(user => {
          this.user = user;
        });
      }
    
      canDeactivate() {
        // Check if user can leave
        if (this.hasUnsavedChanges()) {
          return confirm('You have unsaved changes. Are you sure you want to leave?');
        }
        return true;
      }
    
      deactivate() {
        // Cleanup when leaving
        this.cleanup();
      }
    }
    // Router configuration - declarative and type-safe
    import { route } from '@aurelia/router';
    
    @route({
      routes: [
        { path: ['', 'home'], component: HomePage, title: 'Home' },
        { path: 'users/:id', component: UserDetailPage, title: 'User Details' },
        { path: 'admin/*', component: AdminArea, title: 'Admin' }
      ]
    })
    export class MyApp {
      // Router is automatically available
    }
    
    // Enhanced lifecycle hooks with better typing
    import { IRouteViewModel, Params, RouteNode, NavigationInstruction } from '@aurelia/router';
    
    export class UserDetailPage implements IRouteViewModel {
      user: User;
    
      // Renamed and enhanced lifecycle hooks
      canLoad(
        params: Params,
        next: RouteNode,
        current: RouteNode | null
      ): boolean | NavigationInstruction | Promise<boolean | NavigationInstruction> {
    
        if (!this.authService.isAuthenticated()) {
          return { component: 'login', parameters: { returnUrl: next.path } };
        }
        return true;
      }
    
      async loading(params: Params, next: RouteNode, current: RouteNode | null): Promise<void> {
        // Load data - much cleaner async support
        this.user = await this.userService.getUser(params.id);
    
        // Set dynamic title based on loaded data
        next.setTitle(`User: ${this.user.name}`);
      }
    
      canUnload(next: RouteNode | null, current: RouteNode): boolean | Promise<boolean> {
        if (this.hasUnsavedChanges()) {
          return this.platform.window.confirm(
            'You have unsaved changes. Are you sure you want to leave?'
          );
        }
        return true;
      }
    
      unloading(next: RouteNode | null, current: RouteNode): void {
        this.cleanup();
      }
    }
    
    // Advanced routing with lazy loading and guards
    @route({
      routes: [
        {
          path: 'dashboard',
          component: import('./pages/dashboard'),  // Lazy loading
          title: 'Dashboard',
          data: { requiresAuth: true }  // Route metadata
        },
        {
          path: 'users/:id/edit',
          component: UserEditPage,
          title: 'Edit User',
          data: { requiresPermission: 'users:edit' }
        }
      ]
    })
    export class MyApp {
      // Global navigation hooks can be defined here
    }
    <template>
      <!-- Basic binding -->
      <input value.bind="name" />
      <input value.two-way="email" />
      <span textcontent.bind="message"></span>
    
      <!-- Event binding -->
      <button click.trigger="save()">Save</button>
      <button click.delegate="delete($event)">Delete</button>
    
      <!-- Class binding -->
      <div class="card ${isActive ? 'active' : ''}">Content</div>
    
      <!-- Style binding -->
      <div style="color: ${textColor}; background: ${bgColor}">Styled</div>
    
      <!-- Conditional rendering -->
      <div if.bind="showDetails">Details here</div>
      <div show.bind="isVisible">Visible content</div>
    
      <!-- Repeating -->
      <ul>
        <li repeat.for="item of items">${item.name}</li>
      </ul>
    
      <!-- Value converters -->
      <span>${date | dateFormat:'MM/dd/yyyy'}</span>
      <input value.bind="amount | number:'2.0-2'">
    
      <!-- Binding behaviors -->
      <input value.bind="query & debounce:500">
      <div scroll.bind="scrollPosition & throttle:100">
    </template>
    // Computed properties needed @computedFrom
    import { computedFrom } from 'aurelia-framework';
    
    export class UserProfile {
      firstName: string;
      lastName: string;
    
      @computedFrom('firstName', 'lastName')
      get fullName() {
        return `${this.firstName} ${this.lastName}`;
      }
    }
    <!-- Enhanced binding with new features -->
    
    <!-- Basic binding - same as v1 -->
    <input value.bind="name" />
    <input value.two-way="email" />
    <span textcontent.bind="message"></span>
    
    <!-- Event binding - enhanced -->
    <button click.trigger="save()">Save</button>
    <!-- Event binding can now return functions -->
    <button click.trigger="getClickHandler()">Dynamic Handler</button>
    
    <!-- CSS class binding - much easier! -->
    <div class="card" active.class="isActive" loading.class="isLoading">
      Content
    </div>
    
    <!-- Style binding - same syntax -->
    <div style="color: ${textColor}; background: ${bgColor}">Styled</div>
    
    <!-- Conditional rendering - same -->
    <div if.bind="showDetails">Details here</div>
    <div show.bind="isVisible">Visible content</div>
    
    <!-- Lambda expressions in templates! -->
    <ul>
      <li repeat.for="user of users.filter(u => u.isActive)">
        ${user.name}
      </li>
    </ul>
    
    <!-- Array method observation -->
    <p>Total: ${items.reduce((sum, item) => sum + item.price, 0)}</p>
    
    <!-- Value converters - same syntax -->
    <span>${date | dateFormat:'MM/dd/yyyy'}</span>
    <input value.bind="amount | number:'2.0-2'">
    
    <!-- Binding behaviors - same syntax -->
    <input value.bind="query & debounce:500">
    <div scroll.bind="scrollPosition & throttle:100">
    
    <!-- Enhanced ref binding -->
    <input ref="emailInput" value.bind="email">
    <custom-component component.ref="myComponent">
    </custom-component>
    // Computed properties - no decorator needed!
    export class UserProfile {
      firstName: string;
      lastName: string;
    
      // Automatically computed - Aurelia 2 figures it out
      get fullName() {
        return `${this.firstName} ${this.lastName}`;
      }
    
      // Complex computations work automatically
      get filteredItems() {
        return this.items
          .filter(item => item.isActive)
          .sort((a, b) => a.name.localeCompare(b.name));
      }
    }
    import { useShadowDOM } from '@aurelia/runtime-html';
    
    @useShadowDOM({ mode: 'open' })
    @customElement({
      name: 'isolated-component',
      template: '<div class="content"><slot></slot></div>',
      style: '.content { padding: 20px; color: blue; }' // Encapsulated styles!
    })
    export class IsolatedComponent {
      // Styles won't leak out, external styles won't leak in
    }
    import { attributePattern } from '@aurelia/template-compiler';
    
    // Enable Angular-like syntax: <input [disabled]="isDisabled">
    @attributePattern({ pattern: '[PART]', symbols: '[]' })
    export class AngularStyleBinding {
      ['[PART]'](rawName: string, rawValue: string, parts: string[]): AttrSyntax {
        return new AttrSyntax(rawName, rawValue, parts[0], 'to-view');
      }
    }
    import { customElement, processContent, viewResources } from '@aurelia/runtime-html';
    
    @processContent((node, platform) => {
      // Transform template content at compile time
      const slots = node.querySelectorAll('template[slot]');
      // Process slots, add default content, etc.
      return true; // Continue processing
    })
    @customElement({
      name: 'enhanced-card',
      template: `
        <div class="card">
          <header class="card-header">
            <slot name="header">Default Header</slot>
          </header>
          <div class="card-body">
            <slot>Default Content</slot>
          </div>
        </div>
      `,
      style: `
        .card { border: 1px solid #ccc; border-radius: 4px; }
        .card-header { background: #f5f5f5; padding: 1rem; }
        .card-body { padding: 1rem; }
      `
    })
    export class EnhancedCard {
      // Advanced component features
    }
    import { watch } from '@aurelia/runtime-html';
    
    export class SearchComponent {
      searchTerm: string = '';
      results: SearchResult[] = [];
    
      @watch('searchTerm')
      async searchTermChanged(newValue: string, oldValue: string) {
        if (newValue.length > 2) {
          this.results = await this.searchService.search(newValue);
        } else {
          this.results = [];
        }
      }
    }