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Node.js Design Patterns

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NodeJS in a Nutshell

Introduction The Node.js Philosophy How Node.js Works JavaScript in Node.js Summary Quiz

The Module System

Introduction CommonJS Modules The Resolving Algorithm Module Definition Patterns (I)Module Definition Patterns (II)ESM: ECMAScript Modules ESM: Named Exports and Imports ESM: Default, Mixed, and Async Module Loading in Depth Modifying Other Modules ESM and CommonJS Differences and Interoperability Summary Quiz

Callbacks and Events

Introduction The Callback Pattern: Continuation-Passing Style (CPS)The Callback Pattern: Synchronous vs. Asynchronous (I)The Callback Pattern: Synchronous vs. Asynchronous (II)The Callback Pattern: Node.js Conventions The Observer Pattern: The EventEmitter Class The Observer Pattern: Observable Objects The Observer Pattern: Synchronous and Asynchronous Events EventEmitter vs. Callbacks Summary Exercise: A Simple Event Exercise: Ticker Exercise: A Simple Modification Exercise: Playing with Errors

Asynchronous Control Flow Patterns with Callbacks

Introduction Difficulties of Asynchronous Programming: Web Spider Callback Best Practices: Callback Discipline Sequential Execution: Web Spider Version 2 Sequential Execution: Crawling of Links Sequential Execution: The Pattern Parallel Execution: Web Spider Version 3 Parallel Execution: The Pattern Limited Parallel Execution Globally Limiting Concurrency Web Spider Version 4 The Async Library Summary Exercise: File Concatenation Exercise: List Files Recursively Exercise: Recursive Find

Asynchronous Control Flow Patterns with Promises and Async/Await

Introduction Promises Sequential Execution and Iteration Parallel Execution Limited Parallel Execution and the TaskQueue class Updating the Web Spider Async/Await Pair in Asynchronous Code Error Handling with async/await Sequential Execution and Iteration with Async/Await Parallel Execution Using Async/Await and Promise.all()Limited Parallel Execution The Problem with Infinite Recursive Promise Resolution Chains Summary Exercise: Dissecting Promise.all()Exercise: TaskQueue with Promises Exercise: Producer-Consumer with Promises Exercise: An Asynchronous map()

Coding with Streams

Spatial Efficiency

Time Efficiency

Getting Started with Streams

Readable Streams: Non-Flowing and Flowing Modes

Implementing Readable Streams

Readable Streams: Simplified Construction and Iterables

Writable Streams: Writing a Stream and Backpressure

Writable Streams: Implementation

Implementing Transform Streams

Filtering and Aggregating Data with Transform Streams

PassThrough Streams

Pipes and Error Handling

Better Error Handling with pipeline()

Asynchronous Control Flow Patterns with Streams

Unordered Parallel Execution

Unordered Limited Parallel Execution

Asynchronous Control Flow Patterns: Ordered Parallel Execution

Piping Patterns: Combining Streams

Piping Patterns: Forking Streams

Merging Streams: Merging Text Files

Piping Patterns: Multiplexing and Demultiplexing

Piping Patterns: Multiplexing and Demultiplexing Object Streams

Exercise: Data Compression Efficiency

Exercise: Stream Data Processing

Creational Design Patterns

Introduction Factory Pattern: Decoupling Object Creation Factory Pattern: Encapsulation and Simple Code Profiler Builder Pattern Builder Pattern: Implementing a URL Object Builder Revealing Constructor Singleton Pattern Wiring Modules: Singleton Dependencies Wiring Modules: Dependency Injection Summary Exercise: Console Color Factory Exercise: Request Builder Exercise: A Tamper-Free Queue

Structural Design Patterns

Introduction Proxy Pattern: Techniques for Implementing Proxies (I)Proxy Pattern: Techniques for Implementing Proxies (II)Proxy Pattern: Creating a Logging Writable Stream Proxy Pattern: Change Observer pattern with Proxy Decorator Pattern Decorating a LevelUP database The Line between the Proxy and Decorator Pattern The Adapter Pattern Summary Exercise: HTTP Client Cache Exercise: Timestamped Logs Exercise: Colored Console Output Exercise: A Virtual Filesystem Exercise: The Lazy Buffer

Behavioral Design Patterns

Introduction Strategy Pattern State Pattern Implementing a Basic Failsafe Socket Template Pattern Iterator Pattern The Iterable Protocol Iterator Built-Ins Generators Pattern Async Iterators Async Generators Middleware Pattern Creating a Middleware Framework for ZeroMQ Implementing the Middleware to Process Messages Command Pattern Implementation of Command Pattern Summary Exercise: Logging with Strategy Exercise: Logging with Template Exercise: Warehouse Item Exercise: Logging with Middleware

Universal JavaScript for Web Applications

Introduction Sharing Code with the Browser Module Bundlers Using Webpack Fundamentals of Cross-Platform Development (I)Fundamentals of Cross-Platform Development (II)Fundamentals of Cross-Platform Development (III)A Brief Introduction to React Alternatives to the react.createElement() Method Stateful Components Creating a Universal JavaScript App Server-Side Rendering Asynchronous Data Retrieval Universal Data Retrieval Implementing Async Pages Summary Quiz

Advanced Recipes

Introduction Dealing with Asynchronously Initialized Components Pre-Initialization Queues Asynchronous Request Batching and Caching An API Server without Caching or Batching Batching and Caching with Promises Canceling Asynchronous Operations Cancelable Async Functions with Generators Running CPU-Bound Tasks Interleaving with the setImmediate Function Using External Processes (I)Using External Processes (II)Using Worker Threads Summary Exercise: Proxy with Pre-Initialization Queues Exercise: Batching and Caching with Callback Exercise: Deep Async Cancelable

Scalability and Architectural Patterns

Introduction An Introduction to Application Scaling Cloning and Load Balancing Building a Simple HTTP Server Zero-Downtime Restart Dealing with Stateful Communications Scaling with a Reverse Proxy Dynamic Horizontal Scaling Peer-to-Peer Load Balancing Scaling Applications Using Containers (I)Scaling Applications Using Containers (II)Decomposing Complex Applications Integration Patterns in a Microservice Architecture Summary Quiz

Messaging and Integration Patterns

Introduction Fundamentals of a Messaging System Publish/Subscribe Pattern Publish/Subscribe Pattern Using Redis Peer-To-Peer Publish/Subscribe with ZeroMQ Reliable Message Delivery with Queues Reliable Messaging with Streams Task Distribution Patterns Task Distribution Tasks with ZeroMQ Pipelines and Competing Consumers in AMQP Distributing Tasks with Redis Streams Request/Reply Patterns Return Address Summary Quiz

Conclusion

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Untitled Masterpiece

Learn how to merge streams using piping patterns.

Merging is the opposite operation to forking and involves piping a set of Readable streams into a single Writable stream, as shown in the illustration given below.

Merging streams

Merging streams

Merging multiple streams into one is, in general, a simple operation; however, we have to pay attention to the way we handle the end event because piping using the default options (according to which {end:true}) causes the destination stream to end as soon as one of the sources ends. This can often lead to an error because the other active sources continue to write to an already terminated stream.

The solution to ...