Two-way Filters example code does'nt work

http://vuejs.org/guide/custom-filter.html#Two-way_Filters

This doesn't work.

Vue.filter('currencyDisplay', {
  currencyDisplay: {
    // model -> view
    // formats the value when updating the input element.
    read: function(val) {
      return '$'+val.toFixed(2)
    },
    // view -> model
    // formats the value when updating the data.
    write: function(val, oldVal) {
      var number = +val.replace(/[^\d.]/g, '')
      return isNaN(number) ? 0 : number
    }
  }
})

This is work.

Vue.filter('currencyDisplay', {
    // model -> view
    // formats the value when updating the input element.
    read: function(val) {
      return '$'+val.toFixed(2)
    },
    // view -> model
    // formats the value when updating the data.
    write: function(val, oldVal) {
      var number = +val.replace(/[^\d.]/g, '')
      return isNaN(number) ? 0 : number
    }
  }
})

[yyx990803]

Thanks!