DropdownList multiple disabled items

DisabledItemList.jsx

var DisabledList = React.createClass({

  // proptypes tell the parent widget what to pass into it
  // the DropdownList will inspect propTypes and _.pick() those keys to pass in
  propTypes: {
    disabledItems: React.PropTypes.array,
    ...List.type.propTypes,
  },

  componentWillMount(){
    var parent = this

    // we need to use a closure to allow the list item to know whether its disabled or not.
    // do this infrequently though b/c it is costly, hence we cache it in state
    this.setState({
      listItem: React.createClass({
        render() {
          // add css rules to make it look "disabled"
          var classes = parent.isDisabled(this.props.item) ? 'rw-state-disabled' : ''

          return <div className={classes}>{this.props.item.name}</div>
        }
      })
    })
  },

  render() {
    return (
      <List {...this.props} 
        ref='list' 
        itemComponent={this.state.listItem}
        onSelect={ item => {
          if (!this.isDisabled(item))
            this.props.onSelect(item) // only allow selection of non-disabled items
        }}
      />
    )
  },

  isDisabled(item){
    return this.props.disabledItems 
      && this.props.disabledItems.some( id => id === item.id )
  },

  // Get the next item in the sequence, but keep going if the next one is disabled
  move(dir, item){
    var stop = dir === 'next' ? this.refs.list.last() : this.refs.list.first()
      , next = this.refs.list[dir](item);
    
    while( next !== stop && this.isDisabled(next)) 
      next = this.refs.list[dir](next)

    return this.isDisabled(next) ? item  : next
  },


  // -- These are the basic List methods that must be implemented
  first() {
    this.move('next', null)
  },

  last() {
    this.move('prev', null)
  },

  next(...args){
    var item = this.refs.list.next(...args)

    return this.move('next', item)
  },

  prev(...args){
    var item = this.refs.list.prev(...args)

    return this.move('prev', item)
  }

})

DropdownList.jsx

var MyDropdownList = React.createClass({

  render(){
    var disabled = this.props.disabled && !Array.isArray(this.props.disabled)
      , items = Array.isArray(this.props.disabled) ? this.props.disabled : [];
      
    return (
      <DropdownList {...this.props}
        disabled={disabled}
        listComponent={DisabledList} 
        disabledItems={items}
      />
    )
  }
})