js-gof

GoF Patterns

• Use structural composition over inheritance
• Use multiparadigm code and contract-programming
• Use domain-specific languages (DSLs), prefer declarative way
• Separate and do not mix system and domain code
• Use GRASP and SOLID principles; especially reduce coupling
• Remember about referential transparency
• Prefer platform-agnostic code
• Implement isolation and layer borders with IoC & DI
• Use object/Map lookup for Strategy and polymorphic/dynamic dispatch
• Keep patterns simple
• Do not over-engineer for the sake of the pattern name

Creational patterns

Abstract factory

Creates related objects belonging to one family without specifying their concrete classes, e.g., UI components for different platforms.

Refs: https://github.com/HowProgrammingWorks/AbstractFactory

const dataAccess = {
  fs: {
    createDatabase: (...args) => new FileStorage(...args),
    createCursor: (...args) => new FileLineCursor(...args),
  },
  minio: {
    // factories collection for minio
  },
  // other implementations
};

// Usage

const accessLayer = dataAccess.fs;
const storage = accessLayer.createDatabase('./storage.dat');
const cursor = accessLayer.createCursor({ city: 'Roma' }, storage);
for await (const record of cursor) {
  console.dir(record);
}

Builder

Step-by-step assembly of a complex configurable object, often using chaining, e.g., Query Builder or Form Generator.

Refs: https://github.com/HowProgrammingWorks/Builder

class QueryBuilder {
  #options;

  constructor(table) {
    this.#options = { table, where: {}, limit: null, order: null };
  }

  where(cond) {
    Object.assign(this.#options.where, cond);
    return this;
  }

  order(field) {
    this.#options.order = field;
    return this;
  }

  limit(n) {
    this.#options.limit = n;
    return this;
  }

  build() {
    return { ...this.#options };
  }
}

const query = new QueryBuilder('User')
  .where({ active: true })
  .order('name')
  .limit(10)
  .build();