Node.js Array subclass

SubArray.js

// For context on difficulties of subclassing Array:
// See, http://perfectionkills.com/how-ecmascript-5-still-does-not-allow-to-subclass-an-array/

var sandbox = {};
require('vm').createScript('SubArray = Array').runInNewContext(sandbox);

var SubArray = sandbox.SubArray;
console.log(SubArray);
SubArray.prototype.__proto__ = {
  __proto__: Array.prototype,

  // Your sandboxed array prototype properties here.
  custom: function() {
    console.log('custom');
  }
};

var x = new SubArray(1,2,3);

x instanceof SubArray            // true
x instanceof Array               // true
x.length = 5
x.push(5)                        // x = [1,2,3,null,null,5]
x.length = 2                     // x = [1,2]
[4,5,6].concat(x)                // [4,5,6,1,2,3]

// etc...

See https://gist.github.com/1321777