gistfile1.js

'use strict'
let Buffer = function(a,b)
{
  if (!(this instanceof Buffer))
    return new Buffer(a, b)
  let self = Uint8Array.call(this,a,b)
  self.__proto__ = Buffer.prototype
  return self
}
Buffer.prototype = Object.create(Uint8Array.prototype, Buffer.prototype)
Buffer.prototype.x = 1
 
let x = new Buffer(12)
console.log(x instanceof Buffer)
console.log(x instanceof Uint8Array)
console.log(x.slice)
console.log(x.x)