An attempt at creating an array in javascript without using Array.

javascript-array-impl.js

var equal = require('assert').equal;

  var instance = this;
  var lengthFacade = 0;

  this.push = function(value){
    this[getLength()] = value;
  };

  Object.defineProperty(this, 'length', {
    get: getLength,
    set: setLength
  });

  function getLength(){
    var highestProp = getHighestProp();
    return typeof highestProp === 'number' && highestProp >= lengthFacade ? highestProp + 1 : lengthFacade;
  }

  function setLength(amount){
    var length = getLength();
    var starting = amount > length ? amount : length;

    forNumericProps(function(prop){
      if(amount <= prop)delete instance[prop];
    });

    lengthFacade = amount;
  }

  function getHighestProp(){
    var highest;
    forNumericProps(function(prop){
      if(!highest || prop > highest)highest = prop;
    });
    return highest;
  }

  function forNumericProps(cb){
    var prop;
    for(prop in instance){
      if(/^[0-9]+$/.test(prop))cb(parseInt(prop));
    }
  }
}

var a = new MyArray();
equal(a.length, 0);
a.push(5);
equal(a[0], 5);
equal(a.length, 1);
a.length = 0;
equal(a.length, 0);
a[23452345] = 5;
equal(a[23452345], 5);
equal(a.length, 23452346);
a.length = 3;
equal(a.length, 3);
a[2] = 5;
equal(a[2], 5);
delete a[2];
equal(a.length, 3);
console.log('All passed!');