Pure and Impure Pipes

Lesson content

🎯 Goal Understand Pure and Impure Pipes , why it matters, and how to apply it in a production Angular application. What is Pure and Impure Pipes? Understand pipe execution behavior and its performance impact. Simple definition: Understand pipe execution behavior and its performance impact. Why Do We Need It? Keep the application easier to understand and maintain. Use Angular APIs in a predictable and testable way. Avoid common performance, lifecycle, and architecture mistakes. Real-Life Example Think of an Angular application as a well-organized office. Each feature has a clear responsibility, shared services provide common facilities, and communication follows defined channels. Application │ ▼ Pure and Impure Pipes │ ▼ Predictable Angular Behavior Code Example @Pipe({ name: 'shortText', standalone: true }) export class ShortTextPipe implements PipeTransform { transform(value: string): string { return value.slice(0, 20); } } How It Works Requirement │ ▼ Choose Angular API │ ▼ Implement Typed Logic │ ▼ Render / React │ ▼ Test and Optimize Interview Questions What is Pure and Impure Pipes? Understand pipe execution behavior and its performance impact. What should be considered in production? Consider typing, cleanup, error handling, accessibility, security, testability, and performance. Best Practices ✅ Keep examples and responsibilities focused. ✅ Prefer strongly typed public APIs. ✅ Use framework-managed cleanup whenever possible. ✅ Test user-visible behavior rather than private implementation details. ❌ Do not introduce complexity without a concrete requirement. Key Points Pure and Impure Pipes should solve a clear application problem. Modern Angular favors standalone, typed, and reactive APIs. Production code must include errors, cleanup, tests, and performance considerations. 🧠 Easy Formula Clear Requirement + Correct Angular API + Strong Typing + Cleanup and Tests = Maintainable Angular Feature