node-decorators

What are Decorators

Just like we have @annotations in Java Universe (Spring), we have @decorators in NodeJS (TypeScript) universe. These 2 enable us to carve out redundant code like caching, logging, validity of parameters etc.

From TypeScriptLang

A Decorator is a special kind of declaration that can be attached to a class declaration, method, accessor, property, or parameter. Decorators use the form @expression , where expression must evaluate to a function that will be called at runtime with information about the decorated declaration.

Why use Decorators

1. Abstract out redundant code
2. Keep business logic clean
3. Improve developer productivity

Look at this basic example

const getUsernameById(String userId){
  const userName = CACHE.get("bucket", userId);
  if(!_.isNil(userName)) {
    return userName;
  }
  
  const user = UserModel.getById(userId);
  CACHE.set("bucket", userId, user.name);
  Log.info(
    method: "getUsernameById"
    key_1: "userId",
    key_1_value: userId,
    key_2: "userName",
    key_2_value: userName
  )
  return user.name;
}

This can be reduced to following using decorators

@Cacheable
@Loggable
const getUsernameById(String userId){
  const user = UserModel.getById(userId);
  return user.name;
}

How to use this project

npm -v //6.14.15
node -v //v14.18.2

git clone https://github.com/thekosmix/node-decorators
cd node-decorators
npm i
npm run build
npm start

Features

1. Caching - concated method arguments as key and method response as value
2. Logging - takes argument logRequest & logResponse as boolean and extra arguments to log along with requests and responses