cutesy little Object storage with Array like functionality

list.js

var List = function () {
  this.h = {};
  this.i = [];
};

List.prototype.set = function (key, val, unshift) {
  var op = unshift ? "unshift" : "push";

  this.h[key] = val;

  Array.prototype[op].call(this.i, key);
};

List.prototype.get = function (key) {
  return this.h[key];
};

List.prototype.split = function (by) {
  return this.join("").split(by);
};

List.prototype.join = function (by) {
  var str = "";
  this.i.forEach(function (key) {
    str += this.h[key] + by;
  }.bind(this));
  return str;
};

List.prototype.pop = function () {
  var key = this.i.pop();
  var val = this.h[key];
  delete this.h[key];
  return val;
};

List.prototype.shift = function () {
  var key = this.i.shift();
  var val = this.h[key];
  delete this.h[key];
  return val;
};

List.prototype.push = function (val) {
  this.set(this.i.length, val); // TODO generate random chars?
};

List.prototype.unshift = function () {
  this.set(this.i.length, val, true); // TODO generate random chars?
};

module.exports = List;