title: Map dat.GUI Dropdown Menu Strings to Values
body: <p>When generating a dat.GUI dropdown menu, I give an array of strings that will be the dropdown menu entries. Upon a user selection, the corresponding data property is updated to be the selected menu string.</p>
  
  <p>Is there a way to separate the strings in the menu from the corresponding values (which could be of any type)?<br>
  For example, say my menu is <code>['King', 'Queen', 'Rook']</code>, I'd like my property to get the values resp. <code>['A','B','C']</code> or <code>[-1, 9, 5]</code>.  </p>