array.js

Array.prototype.__defineGetter__('first', function() {
  return this[0];
});

Array.prototype.__defineGetter__('last', function() {
  return this[this.length - 1];
});

Array.prototype.__defineSetter__('first', function(val) {
  this[0] = val;
});

Array.prototype.__defineSetter__('last', function(val) {
  if (this.length) {
    this[this.length - 1] = val;
  } else {
    this[0] = val;
  }
});