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Design Patterns cheat sheet & developer notes

Design Patterns cheat sheet and 3 curated developer notes — core concepts, patterns, and interview prep. Maintained by the DevRecall team.

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01 · Design Patterns

Behavioral Patterns

Behavioral Patterns. Observer. Define a one-to-many dependency so when one object changes state, all dependents are notified.. interface Observer<T> { update(data: T): void; } class EventEmitter<T> { private observers: O…

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02 · Design Patterns

Creational & Structural Patterns

Creational & Structural Patterns. Singleton. Ensure a class has only one instance and provide a global access point.. // Module-level singleton (TypeScript/Node.js — common pattern) class DatabaseConnection { private sta…

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03 · Design Patterns

Interview Questions

Design Patterns Interview Questions. Q: What are the three categories of design patterns?. Creational — object creation (Singleton, Factory, Abstract Factory, Builder, Prototype). Structural — object composition (Adapter…

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TypeScriptgeneral

Interview Questions

TypeScript Interview Questions. Comprehensive TypeScript interview questions covering type system, generics, utility types, and best practices:. Fundamentals. 1. What is TypeScript?. TypeScript is a…

Mar 28, 2026

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TypeScriptgeneral

Advanced Types (Generics & Utility Types)

TypeScript Advanced Types. Generics. // Generic function function identity<T>(arg: T): T { return arg; } const num = identity<number>(42); // Explicit const str = identity('hello'); // Inferred //…

Mar 3, 2026

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