Function Decoration Idea in JS

decorate.js

// function decorating in JS

function ___(wrapper) {
    return function wrap(f) {
      let a = { [f.name] : function(...args) {return wrapper.call(this, f, ...args)} }
      return this[f.name] = a[f.name]
    }
}

function $__(inner) {
  return ___(function(main, ...args) {
    let newargs
    newargs=inner.call(this, ...args)
    if (newargs !== undefined) args = Array.isArray(newargs) ? newargs : [newargs]
    return main.call(this, ...args)
  })
}

function __$(inner) {
  return ___(function(main, ...args) {
    let res = main.call(this, ...args)
    inner.call(this, ...args)
    return res
  })
} 


let log = (...args)=>{
  console.log('Log:'),
  console.log(args)
  //return args.map(x=>x+'(logged)')
}


__$(log)(
function greet(name) {
  console.log('Hello '+name+'!')
}
)

greet('Jon')