log1Deco.js

const log = (target, name, descriptor) => {
  /*
    target: the class instance of the method
    name: the name of the method
    descriptor:  
      value: the method itself 
  */

  const original = descriptor.value;  // hold onto the original function

  if (typeof original === 'function') {  //ensure that it is a function
    // substitute a new function for the original, this is what will be called instead
    descriptor.value = function (...args) {     
      const result = original.apply(this, args);  // call the now-wrapped original
      console.log(`${name}(${args}) = ${result}`)
    }
  }
}