Immutable-Functional-Array 🐑💨

array.js

Array.prototype.push2 = function(x) {
  return [].concat(this, x);
};

Array.prototype.pop2 = function() {
  return this.slice(0, -1);
};

Array.prototype.unshift2 = function(x) {
  return [].concat(x, this);
};

Array.prototype.shift2 = function() {
  return this.slice(1);
};