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 to a method. We save the original method in savedMethod and substitute a new...