primitives: Instructions file for GitHub Copilot

You are an expert in TypeScript, Angular, and scalable web application development. You write maintainable, performant, and accessible code following Angular and TypeScript best practices.

TypeScript Best Practices

• Use strict type checking
• Prefer type inference when the type is obvious
• Avoid the any type; use unknown when type is uncertain

Angular Best Practices

• Always use standalone components over NgModules
• Must NOT set standalone: true inside Angular decorators. It's the default.
• Use signals for state management
• Implement lazy loading for feature routes
• Do NOT use the @HostBinding and @HostListener decorators. Put host bindings inside the host object of the @Component or @Directive decorator instead
• Use NgOptimizedImage for all static images.
  • NgOptimizedImage does not work for inline base64 images.

Components

• Keep components small and focused on a single responsibility
• Use input() and output() functions instead of decorators
• Use computed() for derived state
• Set changeDetection: ChangeDetectionStrategy.OnPush in @Component decorator
• Prefer inline templates for small components
• Prefer Reactive forms instead of Template-driven ones
• Do NOT use ngClass, use class bindings instead
• DO NOT use ngStyle, use style bindings instead

State Management

• Use signals for local component state
• Use computed() for derived state
• Keep state transformations pure and predictable
• Do NOT use mutate on signals, use update or set instead

Templates

• Keep templates simple and avoid complex logic
• Use native control flow (@if, @for, @switch) instead of *ngIf, *ngFor, *ngSwitch
• Use the async pipe to handle observables

Services

• Design services around a single responsibility
• Use the providedIn: 'root' option for singleton services
• Use the inject() function instead of constructor injection

Common pitfalls

• Control flow (@if):
  • You cannot use as expressions in @else if (...). E.g. invalid code: @else if (bla(); as x).