Pure JavaScript Flatten Array extension

gistfile1.js

/**
  @see http://tech.karbassi.com/2009/12/17/pure-javascript-flatten-array/
  // usage
  var given = [[1, [2, [3, [4, [5, [6, [7, [8, [9, [0]]]]]]]]]]];
  var value = given.flatten();
  'value' => [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
 */
Array.prototype.flatten = function () {
  var flat = [], 
    i = 0,
    len = this.length
  ;
  for (; i < l; i++) {
    var type = Object.prototype.toString.call(this[i]).split(' ').pop().split(']').shift().toLowerCase();
    if (type) { 
      flat = flat.concat(/^(array|collection|arguments|object)$/.test(type) ? this[i].flatten() : this[i]); 
    }
  }
  return flat;
}