var Checkout = {
  registerHooks: function(){
    var billing_toggle = $('different_address');
    if( billing_toggle ) {
      Event.observe(billing_toggle, 'click', this.onBillingToggleClick.bind(this));
      this.showBillingForm(billing_toggle.checked);
    }
  },
  showBillingForm: function(visible) {
		visible ? $('billing').show() : $('billing').hide();
  },
  onBillingToggleClick: function(event) {
    var element = Event.element(event);
    this.showBillingForm(element.checked);
  }
}
Event.observe(window, 'load', Checkout.registerHooks.bind(Checkout));