The js is not minified so it is readable. See multiselect-demo.js.
MultiSelect is a form field type that allows selection of one or more items from a list. The list is
populated using a data Store. Items can be reordered via drag and drop if
ddReorder:true is set.
This example has
allowBlank:false so a validation error will appear when the item's selections
are cleared. Validations for
maxSelections can also be applied.
ItemSelector is a specialized MultiSelect field that renders as a pair of MultiSelect field, one with available options and the other with selected options. A set of buttons in between allows items to be moved between the fields and reordered within the selection. Items can also be moved via drag and drop. All the same validations as MultiSelect are supported.