David Walsh's Display Unique Combobox (https://davidwalsh.name/unique-combobox) updated for AMD

example.js

/**
 * An example using the UniqueComboBox defined above. This one creates a combobox with a datastore defined by 
 * dojo/store/Memory and dojo/store/Observable. The UniqueComboBoxMenu provides a way to remove duplicate values 
 * from the list of results returned.
 */

require([
  "dojo/store/Memory",
  "dojo/store/Observable",
  "dijit/form/ComboBox",
  "davidwalsh.form._UniqueComboBoxMenu",
  "dojo/domReady!"
], function (Memory, Observable, ComboBox, _UniqueComboBoxMenu) {
  
  var dataStore = new Observable(new Memory({
    idProperty: "id",
    data: []
  }));
  
  var combo = new ComboBox({
    store: dataStore,
    dropDownClass: _UniqueComboBoxMenu
  }, "myNode");
  
});

UniqueComboBox.js

/**
 * An update on David Walsh's Unique Combobox 
 * Updated for Dojo AMD (tested at v. 1.10)
 * Originally posted: https://davidwalsh.name/unique-combobox
 */
define("davidwalsh.form._UniqueComboBoxMenu", 
["dojo/_base/declare", "dojo/_base/array", "dijit/form/_ComboBoxMenu"], 
function (declare, arrayUtils, _ComboBoxMenu) {
  return declare([_ComboBoxMenu], {
    createOptions: function (results, dataObject, labelFunc) {
      // Cycle through to find uniques
      var uniqueKeys = {}, uniqueItems = [];
      arrayUtils.forEach(results,function(result,index) {
        var label = labelFunc(result);
        if(typeof label != "string") {
          label = label.label;
        }
        if(!uniqueKeys[label]) {
          uniqueKeys[label] = result;
          uniqueItems.push(result);
        }
      });
      
      // Update arguments arr
      arguments[0] = uniqueItems;
        
      // Call inheritance chain for this method, return result
      return this.inherited(arguments);
    }
  })
});