Array.prototype.X.js

Array.prototype.square = function(){
  return Array.from(this, x => x * x)
}
Array.prototype.cube = function(){
  return Array.from(this, x => x * x * x)
}
Array.prototype.average = function(){
  return this.reduce( (a,b) => a + b, 0) / this.length
}
Array.prototype.sum = function(){
  return this.reduce( (a,b) => a + b, 0)
}
Array.prototype.even = function(){
  return this.filter( x => x % 2 == 0 )
}
Array.prototype.odd = function(){
  return this.filter( x => x % 2 != 0 )
}