dxCombobox is a jQuery plugin that allows you to transform any < select > element into an editable combobox.
Pressing any alphanumeric key will transform select box into editable state by creating a text box element. An case insensitive search is performed on the corresponding of the select box, one the users starts to type in this box. When user goes out of the box (on blur/return), if a direct match is found in the < option > then it is selected else a new option is created with the entered text.
$(element).dxCombobox();