Code Style Guide

Developers are advised to use npm init egg --type=simple showcase to generate and observe the recommended project structure and configuration.

# Classify

Old Style:

module.exports = app => {
  class UserService extends app.Service {
    async list() {
      return await this.ctx.curl('https://eggjs.org');
    }
  }
  return UserService;
};

change to:

const Service = require('egg').Service;
class UserService extends Service {
  async list() {
    return await this.ctx.curl('https://eggjs.org');
  }
}
module.exports = UserService;

Additionally, the framework developer needs to change the syntax as follows, otherwise the application developer will have problems customizing base classes such as Service:

const egg = require('egg');

module.exports = Object.assign(egg, {
  Application: class MyApplication extends egg.Application {
    // ...
  }
  // ...
});

# Private Properties & Lazy Initialization

• Private properties are mounted with Symbol.
• The description of Symbol follows the rules of jsdoc, describing the mapped class name + attribute name.
• Delayed initialization.

// app/extend/application.js
const CACHE = Symbol('Application#cache');
const CacheManager = require('../../lib/cache_manager');

module.exports = {
  get cache() {
    if (!this[CACHE]) {
      this[CACHE] = new CacheManager(this);
    }
    return this[CACHE];
  }
};