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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

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

Exercise: Dissecting Promise.all()

Exercise: TaskQueue with Promises

Exercise: Producer-Consumer with Promises

Exercise: An Asynchronous map()

Coding with Streams

Introduction Spatial Efficiency Time Efficiency Composability 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 Duplex Streams Implementing Transform Streams Filtering and Aggregating Data with Transform Streams PassThrough Streams Lazy 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 Summary 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 to adapt the web spider application to implement limited parallel execution.

Web spider v4

Now it’s time to adapt our web spider to implement a limited parallel execution flow using the TaskQueue class we’ve just created.

First, we need to split the spider() function into two functions, one simply initializing a new TaskQueue object and another actually executing the spidering task, which ...