Extendable Array (Implemented in ES6)

fun-r.js

let passThroughs = ['toString', 'toLocaleString', 'unshift']
function FunArr(arr) {
  let fun = {
    i: arr
  }
  for (let proxy of Object.getOwnPropertyNames(Array.prototype)) {
    Object.defineProperty(fun, proxy, {
      get: () => typeof fun.i[proxy] === 'function' ?
        passThroughs.includes(proxy) ?
        (...args) => fun.i[proxy].apply(fun.i,args) :
        (...args) => FunArr(fun.i[proxy].apply(fun.i,args)) :
        fun.i[proxy],
      configurable: true,
      enumerable: false,
    })
  }
  // your array functions go here
  fun.log = () => ((console.log(fun.i), fun))
  return fun
}
let x = FunArr([1,2,3])
console.log(x.length)
console.log(x.i[0])
x.log()
x
  .filter((e)=>true)
  .log() // [1,2,3]
  .filter((e)=>true)

console.log(x.toString()) // 1,2,3