Mastering JavaScript Functional Programming - Second Edition

Chapter 11, Implementing Design Patterns – the Functional Way

11.1. Decorating methods, the future way: As we've already mentioned, decorators aren't a fixed, definitive feature at the moment. However, by following https://tc39.github.io/proposal-decorators/, we can write the following:

const logging = (target, name, descriptor) => {  const savedMethod = descriptor.value;  descriptor.value = function(...args) {    console.log(`entering ${name}: ${args}`);    try {      const valueToReturn = savedMethod.bind(this)(...args);      console.log(`exiting ${name}: ${valueToReturn}`);      return valueToReturn;    } catch (thrownError) {      console.log(`exiting ${name}: threw ${thrownError}`);      throw thrownError;    }  };  return descriptor;};

We want to add a @logging decoration ...