Extension to dojo dnd Selector API

I've had the good fortune of using some dojo drag and drop in a recent project and have been very impressed with the flexibility offered by the APIs. The documentation and tests have been a real help for me in getting drag and drop functionality up and running quickly in my project.

After posting a quick question to the stackoverflow forums, I tried my hand at what Eugene suggested. Here's my attempt:

dojo.provide("my.ext.SelectorMixin");

dojo.require("dojo.dnd.Selector");

dojo.declare(
  "my.ext.SelectorMixin",
  [dojo.dnd.Selector],
  {
    // summary: a mixin for the dojo.dnd.Selector class which adds functionality
    // to shift the currently selected index backwards and forwards. One possible
    // use for this mixin would be to allow a user select different dnd items using
    // the right and left keys.
    
    shift: function(offset, shiftKey) {
      // summary: shifts the currently selected dnd item
      // offset: int: the amount to bump the selection by.
      // shiftKey: Boolean: whether or not this new selection happened when the user was holding
      // down the shift key
      var selectedNodes = this.getSelectedNodes();
      if(selectedNodes && selectedNodes.length) {
        // only delegate to _selectNode if at least one node is selected. If multiple nodes are selected
        // assume that we go with the last selected node.
        this._selectNode(this._getNodeId(selectedNodes[selectedNodes.length - 1].id, offset), shiftKey);
      }
    },
    
    _selectNode: function(nodeId, shiftKey) {
      // summary: selects a node based on nodeId
      // nodeId: String: the id of the node to select
      // shiftKey: Boolean: whether or not this new selection happened when the user was holding
      // down the shift key
      if(!shiftKey) {
        // only clear the selection if the user was not holding down the shift key
        this.selectNone();
      }
      this._addItemClass(dojo.byId(nodeId), "Selected");
      this.selection[nodeId] = 1;
    },
    
    _getNodeId: function(nodeId, offset) {
      // summary: selects a node based on nodeId
      // nodeId: String: the id of the node to select
      // offset: int: the number of nodes to shift the current selection by
      var allNodes = this.getAllNodes(), newId = nodeId;
      for(var i = 0, l = allNodes.length; i < l; i++) {
        var node = allNodes[i]; 
        if(node.id == nodeId) {
          // have a match ... make sure we're not at the start or the end of the dnd set
          if(!((offset == -1 && i == 0) || (i == l - 1 && offset == 1))) {
            // we should be fine to go with the id the user has requested.
            newId = allNodes[i + offset].id;
          }
          break;
        }
      }
      // if we don't get a match, the newId defaults to the currently selected node
      return newId;
    }
  }
);

One very simple use of this extension would be to add key handlers to dojo.doc to listen for right and left keys:

dojo.connect(dojo.doc, "onkeyup", dojo.hitch(this, function(evt) {
  if(evt.keyCode == dojo.keys.RIGHT_ARROW) {
    this.shift(1, evt.shiftKey);
  }
  if(evt.keyCode == dojo.keys.LEFT_ARROW) {
    this.shift(-1, evt.shiftKey);
  }
}));

I'll give a shot at providing some tests for this extension in my next post.